From c34acab1d78ea7727ac6128ae7a7ef12e7b93720 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 16:47:40 -0600
Subject: [PATCH 01/24] Formating.

---
 pipelined/src/ebu/ahbcacheinterface.sv | 10 +++++-----
 pipelined/src/ebu/buscachefsm.sv       | 14 +++++++-------
 pipelined/src/lsu/lsu.sv               | 15 ++++++++-------
 3 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/pipelined/src/ebu/ahbcacheinterface.sv b/pipelined/src/ebu/ahbcacheinterface.sv
index 8b9e29e8..24d529d9 100644
--- a/pipelined/src/ebu/ahbcacheinterface.sv
+++ b/pipelined/src/ebu/ahbcacheinterface.sv
@@ -30,7 +30,7 @@
 
 `include "wally-config.vh"
 
-module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, LOGWPL, LLENPOVERAHBW) (
+module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, AHBWLOGBWPL, LLENPOVERAHBW) (
   input  logic                 HCLK, HRESETn,
   // bus interface controls
   input logic                 HREADY,                  // AHB peripheral ready
@@ -52,7 +52,7 @@ module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, LOGWPL, LLENPOVERAHB
   input logic [1:0]           CacheBusRW,              // Cache bus operation, 01: writeback, 10: fetch
   output logic                CacheBusAck,             // Handshack to $ indicating bus transaction completed
   output logic [LINELEN-1:0]  FetchBuffer,             // Register to hold beats of cache line as the arrive from bus
-  output logic [LOGWPL-1:0]   BeatCount,               // Beat position within the cache line in the Address Phase
+  output logic [AHBWLOGBWPL-1:0]   BeatCount,               // Beat position within the cache line in the Address Phase
   output logic                SelBusBeat,              // Tells the cache to select the word from ReadData or WriteData from BeatCount rather than PAdr
 
   // uncached interface 
@@ -70,7 +70,7 @@ module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, LOGWPL, LLENPOVERAHB
 
   localparam integer           BeatCountThreshold = BEATSPERLINE - 1;  // Largest beat index
   logic [`PA_BITS-1:0]         LocalHADDR;                             // Address after selecting between cached and uncached operation
-  logic [LOGWPL-1:0]           BeatCountDelayed;                       // Beat within the cache line in the second (Data) cache stage
+  logic [AHBWLOGBWPL-1:0]           BeatCountDelayed;                       // Beat within the cache line in the second (Data) cache stage
   logic                        CaptureEn;                              // Enable updating the Fetch buffer with valid data from HRDATA
   logic [`AHBW/8-1:0] 		   BusByteMaskM;                           // Byte enables within a word.  For cache request all 1s
   logic [`AHBW-1:0]            PreHWDATA;                              // AHB Address phase write data
@@ -86,7 +86,7 @@ module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, LOGWPL, LLENPOVERAHB
   end
 
   mux2 #(`PA_BITS) localadrmux(PAdr, CacheBusAdr, Cacheable, LocalHADDR);
-  assign HADDR = ({{`PA_BITS-LOGWPL{1'b0}}, BeatCount} << $clog2(`AHBW/8)) + LocalHADDR;
+  assign HADDR = ({{`PA_BITS-AHBWLOGBWPL{1'b0}}, BeatCount} << $clog2(`AHBW/8)) + LocalHADDR;
 
   mux2 #(3) sizemux(.d0(Funct3), .d1(`AHBW == 32 ? 3'b010 : 3'b011), .s(Cacheable), .y(HSIZE));
 
@@ -111,7 +111,7 @@ module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, LOGWPL, LLENPOVERAHB
   
   flopen #(`AHBW/8) HWSTRBReg(HCLK, HREADY, BusByteMaskM[`AHBW/8-1:0], HWSTRB);
   
-  buscachefsm #(BeatCountThreshold, LOGWPL) AHBBuscachefsm(
+  buscachefsm #(BeatCountThreshold, AHBWLOGBWPL) AHBBuscachefsm(
     .HCLK, .HRESETn, .Flush, .BusRW, .Stall, .BusCommitted, .BusStall, .CaptureEn, .SelBusBeat,
     .CacheBusRW, .CacheBusAck, .BeatCount, .BeatCountDelayed,
 	  .HREADY, .HTRANS, .HWRITE, .HBURST);
diff --git a/pipelined/src/ebu/buscachefsm.sv b/pipelined/src/ebu/buscachefsm.sv
index d9952a45..38618c8a 100644
--- a/pipelined/src/ebu/buscachefsm.sv
+++ b/pipelined/src/ebu/buscachefsm.sv
@@ -28,7 +28,7 @@
 `define BURST_EN 1
 
 // HCLK and clk must be the same clock!
-module buscachefsm #(parameter integer BeatCountThreshold, LOGWPL) (
+module buscachefsm #(parameter integer BeatCountThreshold, AHBWLOGBWPL) (
   input  logic              HCLK,
   input  logic              HRESETn,
 
@@ -47,8 +47,8 @@ module buscachefsm #(parameter integer BeatCountThreshold, LOGWPL) (
   output logic              CacheBusAck,        // Handshack to $ indicating bus transaction completed
   
   // lsu interface
-  output logic [LOGWPL-1:0] BeatCount,          // Beat position within the cache line in the Address Phase
-  output logic [LOGWPL-1:0] BeatCountDelayed,   // Beat within the cache line in the second (Data) cache stage
+  output logic [AHBWLOGBWPL-1:0] BeatCount,          // Beat position within the cache line in the Address Phase
+  output logic [AHBWLOGBWPL-1:0] BeatCountDelayed,   // Beat within the cache line in the second (Data) cache stage
   output logic              SelBusBeat,         // Tells the cache to select the word from ReadData or WriteData from BeatCount rather than PAdr
 
   // BUS interface
@@ -63,7 +63,7 @@ module buscachefsm #(parameter integer BeatCountThreshold, LOGWPL) (
 
   (* mark_debug = "true" *) busstatetype CurrState, NextState;
 
-  logic [LOGWPL-1:0] NextBeatCount;
+  logic [AHBWLOGBWPL-1:0] NextBeatCount;
   logic              FinalBeatCount;
   logic [2:0]        LocalBurstType;
   logic              BeatCntEn;
@@ -98,11 +98,11 @@ module buscachefsm #(parameter integer BeatCountThreshold, LOGWPL) (
 
   // IEU, LSU, and IFU controls
   // Used to store data from data phase of AHB.
-  flopenr #(LOGWPL) BeatCountReg(HCLK, ~HRESETn | BeatCntReset, BeatCntEn, NextBeatCount, BeatCount);  
-  flopenr #(LOGWPL) BeatCountDelayedReg(HCLK, ~HRESETn | BeatCntReset, BeatCntEn, BeatCount, BeatCountDelayed);
+  flopenr #(AHBWLOGBWPL) BeatCountReg(HCLK, ~HRESETn | BeatCntReset, BeatCntEn, NextBeatCount, BeatCount);  
+  flopenr #(AHBWLOGBWPL) BeatCountDelayedReg(HCLK, ~HRESETn | BeatCntReset, BeatCntEn, BeatCount, BeatCountDelayed);
   assign NextBeatCount = BeatCount + 1'b1;
 
-  assign FinalBeatCount = BeatCountDelayed == BeatCountThreshold[LOGWPL-1:0];
+  assign FinalBeatCount = BeatCountDelayed == BeatCountThreshold[AHBWLOGBWPL-1:0];
   assign BeatCntEn = ((NextState == CACHE_WRITEBACK | NextState == CACHE_FETCH) & HREADY & ~Flush) |
                      (NextState == ADR_PHASE & |CacheBusRW & HREADY);
   assign BeatCntReset = NextState == ADR_PHASE;
diff --git a/pipelined/src/lsu/lsu.sv b/pipelined/src/lsu/lsu.sv
index 49988e79..eb3b8caf 100644
--- a/pipelined/src/lsu/lsu.sv
+++ b/pipelined/src/lsu/lsu.sv
@@ -237,12 +237,14 @@ module lsu (
   end else begin
   end
   if (`BUS) begin : bus              
-    localparam integer   LLENWORDSPERLINE = `DCACHE ? `DCACHE_LINELENINBITS/`LLEN : 1; // Number of LLEN words in cacheline
-    localparam integer   LLENLOGBWPL = `DCACHE ? $clog2(LLENWORDSPERLINE) : 1;         // Log2 of ^
-    localparam integer   BEATSPERLINE = `DCACHE ? `DCACHE_LINELENINBITS/`AHBW : 1;     // Number of AHBW words (beats) in cacheline
-    localparam integer   AHBWLOGBWPL = `DCACHE ? $clog2(BEATSPERLINE) : 1;             // Log2 of ^
     if(`DCACHE) begin : dcache
-      localparam integer   LINELEN = `DCACHE ? `DCACHE_LINELENINBITS : `XLEN;          // Number of bytes in cacheline
+      localparam integer   LLENWORDSPERLINE = `DCACHE_LINELENINBITS/`LLEN;             // Number of LLEN words in cacheline
+      localparam integer   LLENLOGBWPL = $clog2(LLENWORDSPERLINE);                     // Log2 of ^
+      localparam integer   BEATSPERLINE = `DCACHE_LINELENINBITS/`AHBW;                 // Number of AHBW words (beats) in cacheline
+      localparam integer   AHBWLOGBWPL = $clog2(BEATSPERLINE);                         // Log2 of ^
+      localparam integer   LINELEN = `DCACHE_LINELENINBITS;                            // Number of bytes in cacheline
+      localparam integer   LLENPOVERAHBW = `LLEN / `AHBW;                              // Number of AHB beats in a LLEN word. AHBW cannot be larger than LLEN. (implementation limitation)
+
       logic [LINELEN-1:0]  FetchBuffer;                                                // Temporary buffer to hold partially fetched cacheline
       logic [`PA_BITS-1:0] DCacheBusAdr;                                               // Cacheline address to fetch or writeback.
       logic [AHBWLOGBWPL-1:0]  BeatCount;                                              // Position within a cacheline.  ahbcacheinterface to cache
@@ -250,7 +252,6 @@ module lsu (
       logic                SelBusBeat;                                                 // ahbcacheinterface selects postion in cacheline with BeatCount
       logic [1:0] 		   CacheBusRW;                                                 // Cache sends request to ahbcacheinterface
 	  logic [1:0] 		   BusRW;                                                      // Uncached bus memory access
-      localparam integer   LLENPOVERAHBW = `LLEN / `AHBW;                              // Number of AHB beats in a LLEN word. AHBW cannot be larger than LLEN. (implementation limitation)
       logic                CacheableOrFlushCacheM;                                     // Memory address is cacheable or operation is a cache flush
       logic [1:0] 		   CacheRWM;                                                   // Cache read (10), write (01), AMO (11)
 	  logic [1:0] 		   CacheAtomicM;                                               // Cache AMO
@@ -272,7 +273,7 @@ module lsu (
         .FetchBuffer, .CacheBusRW, 
         .CacheBusAck(DCacheBusAck), .InvalidateCache(1'b0));
 
-      ahbcacheinterface #(.BEATSPERLINE(BEATSPERLINE), .LINELEN(LINELEN), .LOGWPL(AHBWLOGBWPL), .LLENPOVERAHBW(LLENPOVERAHBW)) ahbcacheinterface(
+      ahbcacheinterface #(.BEATSPERLINE(BEATSPERLINE), .LINELEN(LINELEN), .AHBWLOGBWPL(AHBWLOGBWPL), .LLENPOVERAHBW(LLENPOVERAHBW)) ahbcacheinterface(
         .HCLK(clk), .HRESETn(~reset), .Flush(FlushW),
         .HRDATA, .HWDATA(LSUHWDATA), .HWSTRB(LSUHWSTRB),
         .HSIZE(LSUHSIZE), .HBURST(LSUHBURST), .HTRANS(LSUHTRANS), .HWRITE(LSUHWRITE), .HREADY(LSUHREADY),

From 607c64e0eec114e3f36717e734969af59ab01d85 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 16:52:46 -0600
Subject: [PATCH 02/24] Formating.

---
 pipelined/src/ebu/ahbcacheinterface.sv |  8 ++--
 pipelined/src/ebu/buscachefsm.sv       | 56 ++++++++++++++------------
 2 files changed, 34 insertions(+), 30 deletions(-)

diff --git a/pipelined/src/ebu/ahbcacheinterface.sv b/pipelined/src/ebu/ahbcacheinterface.sv
index 24d529d9..19b51fe2 100644
--- a/pipelined/src/ebu/ahbcacheinterface.sv
+++ b/pipelined/src/ebu/ahbcacheinterface.sv
@@ -4,11 +4,9 @@
 // Written: Ross Thompson ross1728@gmail.com August 29, 2022
 // Modified: 
 //
-// Purpose: Cache/Bus data path.
-// Bus Side logic
-// register the fetch data from the next level of memory.
-// This register should be necessary for timing.  There is no register in the uncore or
-// ahblite controller between the memories and this cache.
+// Purpose: Translates cache bus requests and uncached ieu memory requests into AHB transactions.
+//
+// Documentation: RISC-V System on Chip Design Chapter 9 (Figure 9.8)
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
diff --git a/pipelined/src/ebu/buscachefsm.sv b/pipelined/src/ebu/buscachefsm.sv
index 38618c8a..0b80d529 100644
--- a/pipelined/src/ebu/buscachefsm.sv
+++ b/pipelined/src/ebu/buscachefsm.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // busfsm.sv
 //
-// Written: Ross Thompson ross1728@gmail.com December 29, 2021
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com 
+// Created: December 29, 2021
+// Modified: 18 January 2023 
 //
-// Purpose: Load/Store Unit's interface to BUS for cacheless system
+// Purpose: Controller for cache to AHB bus interface
 // 
+// Documentation: RISC-V System on Chip Design Chapter 9 (Figure 9.9)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -28,34 +31,37 @@
 `define BURST_EN 1
 
 // HCLK and clk must be the same clock!
-module buscachefsm #(parameter integer BeatCountThreshold, AHBWLOGBWPL) (
+module buscachefsm #(
+  parameter integer BeatCountThreshold,              // Largest beat index
+  parameter integer AHBWLOGBWPL                      // Log2 of BEATSPERLINE
+)(
   input  logic              HCLK,
   input  logic              HRESETn,
 
   // IEU interface
-  input  logic              Stall,              // Core pipeline is stalled
-  input  logic              Flush,              // Pipeline stage flush. Prevents bus transaction from starting
-  input  logic [1:0]        BusRW,              // Uncached memory operation read/write control: 10: read, 01: write
-  output logic              BusStall,           // Bus is busy with an in flight memory operation
-  output logic              BusCommitted,       // Bus is busy with an in flight memory operation and it is not safe to take an interrupt
-
-  // ahb cache interface locals.
-  output logic              CaptureEn,          // Enable updating the Fetch buffer with valid data from HRDATA
-
-  // cache interface
-  input  logic [1:0]        CacheBusRW,         // Cache bus operation, 01: writeback, 10: fetch
-  output logic              CacheBusAck,        // Handshack to $ indicating bus transaction completed
+  input  logic              Stall,                   // Core pipeline is stalled
+  input  logic              Flush,                   // Pipeline stage flush. Prevents bus transaction from starting
+  input  logic [1:0]        BusRW,                   // Uncached memory operation read/write control: 10: read, 01: write
+  output logic              BusStall,                // Bus is busy with an in flight memory operation
+  output logic              BusCommitted,            // Bus is busy with an in flight memory operation and it is not safe to take an interrupt
+												    
+  // ahb cache interface locals.				    
+  output logic              CaptureEn,               // Enable updating the Fetch buffer with valid data from HRDATA
+												    
+  // cache interface							    
+  input  logic [1:0]        CacheBusRW,              // Cache bus operation, 01: writeback, 10: fetch
+  output logic              CacheBusAck,             // Handshack to $ indicating bus transaction completed
   
   // lsu interface
   output logic [AHBWLOGBWPL-1:0] BeatCount,          // Beat position within the cache line in the Address Phase
   output logic [AHBWLOGBWPL-1:0] BeatCountDelayed,   // Beat within the cache line in the second (Data) cache stage
-  output logic              SelBusBeat,         // Tells the cache to select the word from ReadData or WriteData from BeatCount rather than PAdr
+  output logic              SelBusBeat,              // Tells the cache to select the word from ReadData or WriteData from BeatCount rather than PAdr
 
   // BUS interface
-  input  logic              HREADY,             // AHB peripheral ready
-  output logic [1:0]        HTRANS,             // AHB transaction type, 00: IDLE, 10 NON_SEQ, 11 SEQ
-  output logic              HWRITE,             // AHB 0: Read operation 1: Write operation 
-  output logic [2:0]        HBURST              // AHB burst length
+  input  logic              HREADY,                  // AHB peripheral ready
+  output logic [1:0]        HTRANS,                  // AHB transaction type, 00: IDLE, 10 NON_SEQ, 11 SEQ
+  output logic              HWRITE,                  // AHB 0: Read operation 1: Write operation 
+  output logic [2:0]        HBURST                   // AHB burst length
 );
   
   typedef enum logic [2:0] {ADR_PHASE, DATA_PHASE, MEM3, CACHE_FETCH, CACHE_WRITEBACK}               busstatetype;
@@ -76,14 +82,14 @@ module buscachefsm #(parameter integer BeatCountThreshold, AHBWLOGBWPL) (
   
   always_comb begin
 	  case(CurrState)
-	    ADR_PHASE:  if (HREADY & |BusRW)                              NextState = DATA_PHASE;
+	    ADR_PHASE:  if (HREADY & |BusRW)                            NextState = DATA_PHASE;
                   else if (HREADY & CacheBusRW[0])                  NextState = CACHE_WRITEBACK;
                   else if (HREADY & CacheBusRW[1])                  NextState = CACHE_FETCH;
                   else                                              NextState = ADR_PHASE;
       DATA_PHASE: if(HREADY)                                        NextState = MEM3;
-		              else                                              NextState = DATA_PHASE;
+		              else                                          NextState = DATA_PHASE;
       MEM3: if(Stall)                                               NextState = MEM3;
-		           else                                                 NextState = ADR_PHASE;
+		           else                                             NextState = ADR_PHASE;
       CACHE_FETCH: if(HREADY & FinalBeatCount & CacheBusRW[0])      NextState = CACHE_WRITEBACK;
                    else if(HREADY & FinalBeatCount & CacheBusRW[1]) NextState = CACHE_FETCH;
                    else if(HREADY & FinalBeatCount & ~|CacheBusRW)  NextState = ADR_PHASE;
@@ -92,7 +98,7 @@ module buscachefsm #(parameter integer BeatCountThreshold, AHBWLOGBWPL) (
                    else if(HREADY & FinalBeatCount & CacheBusRW[1]) NextState = CACHE_FETCH;
                    else if(HREADY & FinalBeatCount & ~|CacheBusRW)  NextState = ADR_PHASE;
                    else                                             NextState = CACHE_WRITEBACK;
-	    default:                                                      NextState = ADR_PHASE;
+	    default:                                                    NextState = ADR_PHASE;
 	  endcase
   end
 

From fc5424fa62386de60a83af1a897412348fadb22a Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 16:58:03 -0600
Subject: [PATCH 03/24] Formatting

---
 pipelined/src/ebu/ahbcacheinterface.sv | 12 +++++++++---
 pipelined/src/ebu/buscachefsm.sv       |  2 +-
 pipelined/src/ifu/ifu.sv               |  2 +-
 pipelined/src/lsu/lsu.sv               |  4 ++--
 4 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/pipelined/src/ebu/ahbcacheinterface.sv b/pipelined/src/ebu/ahbcacheinterface.sv
index 19b51fe2..a127e0fa 100644
--- a/pipelined/src/ebu/ahbcacheinterface.sv
+++ b/pipelined/src/ebu/ahbcacheinterface.sv
@@ -1,8 +1,9 @@
 ///////////////////////////////////////////
 // ahbcacheinterface.sv
 //
-// Written: Ross Thompson ross1728@gmail.com August 29, 2022
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created: August 29, 2022
+// Modified: 18 January 2023
 //
 // Purpose: Translates cache bus requests and uncached ieu memory requests into AHB transactions.
 //
@@ -28,7 +29,12 @@
 
 `include "wally-config.vh"
 
-module ahbcacheinterface #(parameter BEATSPERLINE, LINELEN, AHBWLOGBWPL, LLENPOVERAHBW) (
+module ahbcacheinterface #(
+  parameter integer BEATSPERLINE,  // Number of AHBW words (beats) in cacheline
+  parameter integer AHBWLOGBWPL,   // Log2 of ^
+  parameter integer LINELEN,       // Number of bits in cacheline
+  parameter integer LLENPOVERAHBW  // Number of AHB beats in a LLEN word. AHBW cannot be larger than LLEN. (implementation limitation)
+)(
   input  logic                 HCLK, HRESETn,
   // bus interface controls
   input logic                 HREADY,                  // AHB peripheral ready
diff --git a/pipelined/src/ebu/buscachefsm.sv b/pipelined/src/ebu/buscachefsm.sv
index 0b80d529..97002cab 100644
--- a/pipelined/src/ebu/buscachefsm.sv
+++ b/pipelined/src/ebu/buscachefsm.sv
@@ -28,7 +28,7 @@
 ////////////////////////////////////////////////////////////////////////////////////////////////
 
 `include "wally-config.vh"
-`define BURST_EN 1
+`define BURST_EN 1         // Enables burst mode.  Disable to show the lost performance.
 
 // HCLK and clk must be the same clock!
 module buscachefsm #(
diff --git a/pipelined/src/ifu/ifu.sv b/pipelined/src/ifu/ifu.sv
index 63cea9b4..c0d8837d 100644
--- a/pipelined/src/ifu/ifu.sv
+++ b/pipelined/src/ifu/ifu.sv
@@ -227,7 +227,7 @@ module ifu (
              .NextAdr(PCNextFSpill[11:0]),
              .PAdr(PCPF),
              .CacheCommitted(CacheCommittedF), .InvalidateCache(InvalidateICacheM));
-      ahbcacheinterface #(WORDSPERLINE, LINELEN, LOGBWPL, LLENPOVERAHBW) 
+      ahbcacheinterface #(WORDSPERLINE, LOGBWPL, LINELEN, LLENPOVERAHBW) 
       ahbcacheinterface(.HCLK(clk), .HRESETn(~reset),
             .HRDATA,
             .Flush(FlushD), .CacheBusRW, .HSIZE(IFUHSIZE), .HBURST(IFUHBURST), .HTRANS(IFUHTRANS), .HWSTRB(),
diff --git a/pipelined/src/lsu/lsu.sv b/pipelined/src/lsu/lsu.sv
index eb3b8caf..95f058c3 100644
--- a/pipelined/src/lsu/lsu.sv
+++ b/pipelined/src/lsu/lsu.sv
@@ -242,7 +242,7 @@ module lsu (
       localparam integer   LLENLOGBWPL = $clog2(LLENWORDSPERLINE);                     // Log2 of ^
       localparam integer   BEATSPERLINE = `DCACHE_LINELENINBITS/`AHBW;                 // Number of AHBW words (beats) in cacheline
       localparam integer   AHBWLOGBWPL = $clog2(BEATSPERLINE);                         // Log2 of ^
-      localparam integer   LINELEN = `DCACHE_LINELENINBITS;                            // Number of bytes in cacheline
+      localparam integer   LINELEN = `DCACHE_LINELENINBITS;                            // Number of bits in cacheline
       localparam integer   LLENPOVERAHBW = `LLEN / `AHBW;                              // Number of AHB beats in a LLEN word. AHBW cannot be larger than LLEN. (implementation limitation)
 
       logic [LINELEN-1:0]  FetchBuffer;                                                // Temporary buffer to hold partially fetched cacheline
@@ -273,7 +273,7 @@ module lsu (
         .FetchBuffer, .CacheBusRW, 
         .CacheBusAck(DCacheBusAck), .InvalidateCache(1'b0));
 
-      ahbcacheinterface #(.BEATSPERLINE(BEATSPERLINE), .LINELEN(LINELEN), .AHBWLOGBWPL(AHBWLOGBWPL), .LLENPOVERAHBW(LLENPOVERAHBW)) ahbcacheinterface(
+      ahbcacheinterface #(.BEATSPERLINE(BEATSPERLINE), .AHBWLOGBWPL(AHBWLOGBWPL), .LINELEN(LINELEN),  .LLENPOVERAHBW(LLENPOVERAHBW)) ahbcacheinterface(
         .HCLK(clk), .HRESETn(~reset), .Flush(FlushW),
         .HRDATA, .HWDATA(LSUHWDATA), .HWSTRB(LSUHWSTRB),
         .HSIZE(LSUHSIZE), .HBURST(LSUHBURST), .HTRANS(LSUHTRANS), .HWRITE(LSUHWRITE), .HREADY(LSUHREADY),

From 58a07399a2a3f2082816c57fe43e432dda20e4fe Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 17:03:45 -0600
Subject: [PATCH 04/24] Formatting

---
 pipelined/src/ebu/ahbinterface.sv | 17 +++++++++--------
 pipelined/src/ebu/busfsm.sv       | 23 +++++++++++++----------
 2 files changed, 22 insertions(+), 18 deletions(-)

diff --git a/pipelined/src/ebu/ahbinterface.sv b/pipelined/src/ebu/ahbinterface.sv
index 63449fe8..ff50f54f 100644
--- a/pipelined/src/ebu/ahbinterface.sv
+++ b/pipelined/src/ebu/ahbinterface.sv
@@ -1,15 +1,14 @@
 ///////////////////////////////////////////
 // ahbinterface.sv
 //
-// Written: Ross Thompson ross1728@gmail.com August 29, 2022
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created: August 29, 2022
+// Modified: 18 January 2023
 //
-// Purpose: Cache/Bus data path.
-// Bus Side logic
-// register the fetch data from the next level of memory.
-// This register should be necessary for timing.  There is no register in the uncore or
-// ahblite controller between the memories and this cache.
+// Purpose: Translates LSU simple memory requests into AHB transactions (NON_SEQ).
 // 
+// Documentation: RISC-V System on Chip Design Chapter 6 (Figure 6.21)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -30,7 +29,9 @@
 
 `include "wally-config.vh"
 
-module ahbinterface #(parameter LSU = 0) ( // **** modify to use LSU/ifu parameter to control widths of buses
+module ahbinterface #(
+  parameter LSU = 0                                   // 1: LSU bus width is `XLEN, 0: IFU bus width is 32 bits
+)( 
   input logic 							HCLK, HRESETn,
   // bus interface
   input logic 							HREADY,       // AHB peripheral ready
diff --git a/pipelined/src/ebu/busfsm.sv b/pipelined/src/ebu/busfsm.sv
index 1e8af036..83025322 100644
--- a/pipelined/src/ebu/busfsm.sv
+++ b/pipelined/src/ebu/busfsm.sv
@@ -1,10 +1,13 @@
 ///////////////////////////////////////////
 // busfsm.sv
 //
-// Written: Ross Thompson ross1728@gmail.com December 29, 2021
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created: December 29, 2021
+// Modified: 18 January 2023
 //
-// Purpose: Load/Store Unit's interface to BUS for cacheless system
+// Purpose: Simple NON_SEQ (no burst) AHB controller.
+//
+// Documentation: RISC-V System on Chip Design Chapter 6 (Figure 6.23)
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
@@ -55,13 +58,13 @@ module busfsm (
   
   always_comb begin
 	  case(CurrState)
-	    ADR_PHASE: if(HREADY & |BusRW)  NextState = DATA_PHASE;
-                 else                 NextState = ADR_PHASE;
-      DATA_PHASE: if(HREADY)          NextState = MEM3;
-		          else                    NextState = DATA_PHASE;
-      MEM3: if(Stall)                 NextState = MEM3;
-		    else                          NextState = ADR_PHASE;
-	    default:                        NextState = ADR_PHASE;
+	    ADR_PHASE: if(HREADY & |BusRW) NextState = DATA_PHASE;
+                 else                  NextState = ADR_PHASE;
+      DATA_PHASE: if(HREADY)           NextState = MEM3;
+		          else                 NextState = DATA_PHASE;
+      MEM3: if(Stall)                  NextState = MEM3;
+		    else                       NextState = ADR_PHASE;
+	    default:                       NextState = ADR_PHASE;
 	  endcase
   end
 

From affca27ec4fc24931ede7be073b4f5edb152bc37 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 17:14:37 -0600
Subject: [PATCH 05/24] Formatting

---
 pipelined/src/ebu/controllerinputstage.sv | 47 +++++++++++++----------
 1 file changed, 26 insertions(+), 21 deletions(-)

diff --git a/pipelined/src/ebu/controllerinputstage.sv b/pipelined/src/ebu/controllerinputstage.sv
index e90206ec..681f12bc 100644
--- a/pipelined/src/ebu/controllerinputstage.sv
+++ b/pipelined/src/ebu/controllerinputstage.sv
@@ -1,17 +1,18 @@
 ///////////////////////////////////////////
 // controller input stage
 //
-// Written: Ross Thompson August 31, 2022
-// ross1728@gmail.com
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created:  August 31, 2022
+// Modified: 18 January 2023
 //
 // Purpose: AHB multi controller interface to merge LSU and IFU controls.
 //          See ARM_HIH0033A_AMBA_AHB-Lite_SPEC 1.0
 //          Arbitrates requests from instruction and data streams
 //          Connects core to peripherals and I/O pins on SOC
 //          Bus width presently matches XLEN
-//          Anticipate replacing this with an AXI bus interface to communicate with FPGA DRAM/Flash controllers
 // 
+// Documentation: RISC-V System on Chip Design Chapter 6 (Figure 6.25)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -32,25 +33,29 @@
 
 `include "wally-config.vh"
 
-module controllerinputstage #(parameter SAVE_ENABLED = 1) (
-  input  logic                HCLK,
-  input  logic                HRESETn,
-  input  logic                Save, Restore, Disable,
-  output logic                Request,
+module controllerinputstage #(
+  parameter SAVE_ENABLED = 1           // 1: Save manager inputs if Save = 1, 0: Don't save inputs
+)(
+  input logic 				  HCLK, 
+  input logic 				  HRESETn,
+  input logic 				  Save,     // Two or more managers requesting (HTRANS != 00) at the same time.  Save the non-granted manager inputs
+  input logic 				  Restore,  // Restore a saved manager inputs when it is finally granted
+  input logic 				  Disable,  // Supress HREADY to the non-granted manager
+  output logic 				  Request,  // This manager is making a request
   // controller input
-  input  logic                HWRITEIn,
-  input  logic [2:0]          HSIZEIn,
-  input  logic [2:0]          HBURSTIn,
-  input  logic [1:0]          HTRANSIn,
-  input  logic [`PA_BITS-1:0] HADDRIn,
-  output logic                HREADYOut,
+  input logic [1:0] 		  HTRANSIn,  // Manager input. AHB transaction type, 00: IDLE, 10 NON_SEQ, 11 SEQ
+  input logic 				  HWRITEIn,  // Manager input. AHB 0: Read operation 1: Write operation 
+  input logic [2:0] 		  HSIZEIn,   // Manager input. AHB transaction width
+  input logic [2:0] 		  HBURSTIn,  // Manager input. AHB burst length
+  input logic [`PA_BITS-1:0]  HADDRIn,   // Manager input. AHB address
+  output logic 				  HREADYOut, // Indicate to manager the peripherial is not busy and another manager does not have priority
   // controller output
-  output logic                HWRITEOut,
-  output logic [2:0]          HSIZEOut,
-  output logic [2:0]          HBURSTOut,
-  output logic [1:0]          HTRANSOut,
-  output logic [`PA_BITS-1:0] HADDROut,
-  input  logic                HREADYIn
+  output logic [1:0] 		  HTRANSOut, // Aribrated manager transaction. AHB transaction type, 00: IDLE, 10 NON_SEQ, 11 SEQ
+  output logic 				  HWRITEOut, // Aribrated manager transaction. AHB 0: Read operation 1: Write operation 
+  output logic [2:0] 		  HSIZEOut,  // Aribrated manager transaction. AHB transaction width
+  output logic [2:0] 		  HBURSTOut, // Aribrated manager transaction. AHB burst length 
+  output logic [`PA_BITS-1:0] HADDROut,  // Aribrated manager transaction. AHB address
+  input logic 				  HREADYIn   // Peripherial ready
 );
 
   logic                       HWRITESave;

From 0b244e289c28ee740d14078b39e44e57e65f7e7f Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 17:30:08 -0600
Subject: [PATCH 06/24] Formating.

---
 pipelined/src/ebu/ebu.sv | 64 ++++++++++++++++++++++------------------
 1 file changed, 35 insertions(+), 29 deletions(-)

diff --git a/pipelined/src/ebu/ebu.sv b/pipelined/src/ebu/ebu.sv
index f6792da3..5d8581eb 100644
--- a/pipelined/src/ebu/ebu.sv
+++ b/pipelined/src/ebu/ebu.sv
@@ -10,8 +10,9 @@
 //          Arbitrates requests from instruction and data streams
 //          Connects core to peripherals and I/O pins on SOC
 //          Bus width presently matches XLEN
-//          Anticipate replacing this with an AXI bus interface to communicate with FPGA DRAM/Flash controllers
 // 
+// Documentation: RISC-V System on Chip Design Chapter 6 (Figures 6.25 and 6.26)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -35,42 +36,46 @@
 module ebu (
   input  logic                clk, reset,
   // Signals from IFU
-  input  logic [`PA_BITS-1:0] IFUHADDR, 
-  input  logic [2:0]          IFUHSIZE,
-  input  logic [2:0]          IFUHBURST,
-  input  logic [1:0]          IFUHTRANS,
-  output logic                IFUHREADY, 
+  input  logic [1:0]          IFUHTRANS, // IFU AHB transaction request
+  input  logic [2:0]          IFUHSIZE,  // IFU AHB transaction size
+  input  logic [2:0]          IFUHBURST, // IFU AHB burst length
+  input  logic [`PA_BITS-1:0] IFUHADDR,  // IFU AHB address
+  output logic                IFUHREADY, // AHB peripheral ready gated by possible non-grant
   // Signals from LSU
-  input  logic [`PA_BITS-1:0] LSUHADDR,
+  input  logic [1:0]          LSUHTRANS, // LSU AHB transaction request
+  input  logic                LSUHWRITE, // LSU AHB transaction direction. 1: write, 0: read
+  input  logic [2:0]          LSUHSIZE,  // LSU AHB size
+  input  logic [2:0]          LSUHBURST, // LSU AHB burst length
+  input  logic [`PA_BITS-1:0] LSUHADDR,  // LSU AHB address
   input  logic [`XLEN-1:0]    LSUHWDATA, // initially support AHBW = XLEN
-  input  logic [`XLEN/8-1:0]  LSUHWSTRB,
-  input  logic [2:0]          LSUHSIZE,
-  input  logic [2:0]          LSUHBURST,
-  input  logic [1:0]          LSUHTRANS,
-  input  logic                LSUHWRITE,
-  output logic                LSUHREADY,
-  // add LSUHWSTRB ***
+  input  logic [`XLEN/8-1:0]  LSUHWSTRB, // AHB byte mask
+  output logic                LSUHREADY, // AHB peripheral. Never gated as LSU always has priority
 
   // AHB-Lite external signals
-  (* mark_debug = "true" *) input  logic HREADY, HRESP,
-  (* mark_debug = "true" *) output logic HCLK, HRESETn,
-  (* mark_debug = "true" *) output logic [`PA_BITS-1:0] HADDR, 
-  (* mark_debug = "true" *) output logic [`AHBW-1:0] HWDATA,
-  (* mark_debug = "true" *) output logic [`XLEN/8-1:0] HWSTRB,
-  (* mark_debug = "true" *) output logic HWRITE, 
-  (* mark_debug = "true" *) output logic [2:0] HSIZE,
-  (* mark_debug = "true" *) output logic [2:0] HBURST,
-  (* mark_debug = "true" *) output logic [3:0] HPROT,
-  (* mark_debug = "true" *) output logic [1:0] HTRANS,
-  (* mark_debug = "true" *) output logic HMASTLOCK
+  (* mark_debug = "true" *) output logic HCLK, HRESETn, 
+  (* mark_debug = "true" *) input  logic HREADY,               // AHB peripheral ready
+  (* mark_debug = "true" *) input  logic HRESP,                // AHB peripheral response. 0: OK 1: Error
+  (* mark_debug = "true" *) output logic [`PA_BITS-1:0] HADDR, // AHB address to peripheral after arbitration
+  (* mark_debug = "true" *) output logic [`AHBW-1:0] HWDATA,   // AHB Write data after arbitration
+  (* mark_debug = "true" *) output logic [`XLEN/8-1:0] HWSTRB, // AHB byte write enables after arbitration
+  (* mark_debug = "true" *) output logic HWRITE,               // AHB transaction direction after arbitration
+  (* mark_debug = "true" *) output logic [2:0] HSIZE,          // AHB transaction size after arbitration
+  (* mark_debug = "true" *) output logic [2:0] HBURST,         // AHB burst length after arbitration
+  (* mark_debug = "true" *) output logic [3:0] HPROT,          // AHB protection.  Wally does not use
+  (* mark_debug = "true" *) output logic [1:0] HTRANS,         // AHB transaction request after arbitration
+  (* mark_debug = "true" *) output logic HMASTLOCK             // AHB master lock.  Wally does not use
 );
 
   typedef enum                logic [1:0] {IDLE, ARBITRATE} statetype;
   statetype                   CurrState, NextState;
 
-  logic                       LSUDisable, LSUSelect;
-  logic                       IFUSave, IFURestore, IFUDisable, IFUSelect;
-  logic                       both;
+  logic                       LSUDisable;
+  logic 					  LSUSelect;
+  logic                       IFUSave;
+  logic 					  IFURestore;
+  logic 					  IFUDisable;
+  logic 					  IFUSelect;
+  logic                       both;                       // Both the LSU and IFU request at the same time
 
   logic [`PA_BITS-1:0]        IFUHADDROut;
   logic [1:0]                 IFUHTRANSOut;
@@ -84,7 +89,8 @@ module ebu (
   logic [2:0]                 LSUHSIZEOut;
   logic                       LSUHWRITEOut;
 
-  logic                       IFUReq, LSUReq;
+  logic                       IFUReq;
+  logic 					  LSUReq;
 
   logic                       BeatCntEn;
   logic [4-1:0]               NextBeatCount, BeatCount;

From a6b14eb9eea753b1c23ad26622caec8438cedeb1 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 17:49:19 -0600
Subject: [PATCH 07/24] Formatting.

---
 pipelined/src/ebu/ebu.sv | 61 +++++++++++++++++++++++++---------------
 1 file changed, 38 insertions(+), 23 deletions(-)

diff --git a/pipelined/src/ebu/ebu.sv b/pipelined/src/ebu/ebu.sv
index 5d8581eb..bc162e08 100644
--- a/pipelined/src/ebu/ebu.sv
+++ b/pipelined/src/ebu/ebu.sv
@@ -1,9 +1,9 @@
 ///////////////////////////////////////////
 // abhmulticontroller
 //
-// Written: Ross Thompson August 29, 2022
-// ross1728@gmail.com
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created: August 29, 2022
+// Modified: 18 January 2023
 //
 // Purpose: AHB multi controller interface to merge LSU and IFU controls.
 //          See ARM_HIH0033A_AMBA_AHB-Lite_SPEC 1.0
@@ -93,11 +93,11 @@ module ebu (
   logic 					  LSUReq;
 
   logic                       BeatCntEn;
-  logic [4-1:0]               NextBeatCount, BeatCount;
-  logic                       FinalBeat, FinalBeatD;
+  logic [4-1:0]               NextBeatCount, BeatCount;   // Position within a burst transfer
+  logic                       FinalBeat, FinalBeatD;      // Indicates the last beat of a burst
   logic                       CntReset;
-  logic [3:0]                 Threshold;
-  logic                       IFUReqD;
+  logic [3:0]                 Threshold;                  // Number of beats derived from HBURST
+  logic                       IFUReqD;                    // 1 cycle delayed IFU request. Part of arbitration
   
   
   assign HCLK = clk;
@@ -106,14 +106,16 @@ module ebu (
   // if two requests come in at once pick one to select and save the others Address phase
   // inputs.  Abritration scheme is LSU always goes first.
 
-  // input stage IFU
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // input stages and muxing for IFU and LSU
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+
   controllerinputstage IFUInput(.HCLK, .HRESETn, .Save(IFUSave), .Restore(IFURestore), .Disable(IFUDisable),
     .Request(IFUReq),
     .HWRITEIn(1'b0), .HSIZEIn(IFUHSIZE), .HBURSTIn(IFUHBURST), .HTRANSIn(IFUHTRANS), .HADDRIn(IFUHADDR),
     .HWRITEOut(IFUHWRITEOut), .HSIZEOut(IFUHSIZEOut), .HBURSTOut(IFUHBURSTOut), .HREADYOut(IFUHREADY),
     .HTRANSOut(IFUHTRANSOut), .HADDROut(IFUHADDROut), .HREADYIn(HREADY));
 
-  // input stage LSU
   // LSU always has priority so there should never be a need to save and restore the address phase inputs.
   controllerinputstage #(0) LSUInput(.HCLK, .HRESETn, .Save(1'b0), .Restore(1'b0), .Disable(LSUDisable),
     .Request(LSUReq),
@@ -121,7 +123,7 @@ module ebu (
     .HWRITEOut(LSUHWRITEOut), .HSIZEOut(LSUHSIZEOut), .HBURSTOut(LSUHBURSTOut),
     .HTRANSOut(LSUHTRANSOut), .HADDROut(LSUHADDROut), .HREADYIn(HREADY));
 
-  // output mux //*** rewrite for general number of controllers.
+  // output mux //*** switch to structural implementation
   assign HADDR = LSUSelect ? LSUHADDROut : IFUSelect ? IFUHADDROut : '0;
   assign HSIZE = LSUSelect ? LSUHSIZEOut : IFUSelect ? IFUHSIZEOut: '0; 
   assign HBURST = LSUSelect ? LSUHBURSTOut : IFUSelect ? IFUHBURSTOut : '0; // If doing memory accesses, use LSUburst, else use Instruction burst.
@@ -135,8 +137,13 @@ module ebu (
   assign HWSTRB = LSUHWSTRB;
   // HRDATA is sent to all controllers at the core level.
 
+
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // Aribtration scheme
   // FSM decides if arbitration needed.  Arbitration is held until the last beat of
   // a burst is completed.
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+
   assign both = LSUReq & IFUReq;
   flopenl #(.TYPE(statetype)) busreg(HCLK, ~HRESETn, 1'b1, NextState, IDLE, CurrState);
   always_comb 
@@ -148,8 +155,27 @@ module ebu (
       default:                                                  NextState = IDLE;
     endcase
 
-  // This part is only used when burst mode is supported.
-  // Controller needs to count beats.
+  // basic arb always selects LSU when both
+  // replace this block for more sophisticated arbitration as needed.
+  // Controller 0 (IFU)
+  assign IFUSave = CurrState == IDLE & both;
+  assign IFURestore = CurrState == ARBITRATE;
+  assign IFUDisable = CurrState == ARBITRATE;
+  assign IFUSelect = (NextState == ARBITRATE) ? 1'b0 : IFUReq;
+  // Controller 1 (LSU)
+  // When both the IFU and LSU request at the same time, the FSM will go into the arbitrate state.
+  // Once the LSU request is done the fsm returns to IDLE.  To prevent the LSU from regaining
+  // priority and re issuing the same memroy operation, the delayed IFUReqD squashes the LSU request.
+  // This is necessary because the pipeline is stalled for the entire duration of both transactions,
+  // and the LSU memory request will stil be active.
+  flopr #(1) ifureqreg(clk, ~HRESETn, IFUReq, IFUReqD);
+  assign LSUDisable = CurrState == ARBITRATE ? 1'b0 : (IFUReqD & ~(HREADY & FinalBeatD));
+  assign LSUSelect = NextState == ARBITRATE ? 1'b1: LSUReq;
+
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // Burst mode logic
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+
   flopenr #(4) BeatCountReg(HCLK, ~HRESETn | CntReset | FinalBeat, BeatCntEn, NextBeatCount, BeatCount);  
   assign NextBeatCount = BeatCount + 1'b1;
 
@@ -171,17 +197,6 @@ module ebu (
     endcase
   end
   
-  // basic arb always selects LSU when both
-  // replace this block for more sophisticated arbitration as needed.
-  // Controller 0 (IFU)
-  assign IFUSave = CurrState == IDLE & both;
-  assign IFURestore = CurrState == ARBITRATE;
-  assign IFUDisable = CurrState == ARBITRATE;
-  assign IFUSelect = (NextState == ARBITRATE) ? 1'b0 : IFUReq;
-  // Controller 1 (LSU)
-  assign LSUDisable = CurrState == ARBITRATE ? 1'b0 : (IFUReqD & ~(HREADY & FinalBeatD));
-  assign LSUSelect = NextState == ARBITRATE ? 1'b1: LSUReq;
 
-  flopr #(1) ifureqreg(clk, ~HRESETn, IFUReq, IFUReqD);
   
 endmodule

From 2622f5dfb85fd1d2524211a758b3751d28265152 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 17:56:47 -0600
Subject: [PATCH 08/24] Formatting.

---
 pipelined/src/lsu/amoalu.sv | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/pipelined/src/lsu/amoalu.sv b/pipelined/src/lsu/amoalu.sv
index fa8703b5..46d5e219 100644
--- a/pipelined/src/lsu/amoalu.sv
+++ b/pipelined/src/lsu/amoalu.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // amoalu.sv
 //
-// Written: David_Harris@hmc.edu 10 March 2021
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 10 March 2021
+// Modified: 18 January 2023 
 //
 // Purpose: Performs AMO operations
 // 
+// Documentation: RISC-V System on Chip Design Chapter 14 (Figure ***)
+// 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -26,13 +29,12 @@
 
 `include "wally-config.vh"
 
-// *** this should probably be moved into the LSU because it is instantiated in the D$
-
 module amoalu (
-  input  logic [`XLEN-1:0] srca, srcb,
-  input  logic [6:0]       funct,
-  input  logic [1:0]       width,
-  output logic [`XLEN-1:0] result
+  input  logic [`XLEN-1:0] srca,  // LSU's ReadData *** may want to change signal names.
+  input  logic [`XLEN-1:0] srcb,  // LSU's WriteData
+  input  logic [6:0]       funct, // ALU Operation
+  input  logic [1:0]       width, // Memoy access width
+  output logic [`XLEN-1:0] result // ALU output
 );
 
   logic [`XLEN-1:0] a, b, y;

From 40c0e67930c0371e33c16bfbca8331722b043d41 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:05:11 -0600
Subject: [PATCH 09/24] Formatting.

---
 pipelined/src/lsu/atomic.sv | 34 +++++++++++++++++++---------------
 pipelined/src/lsu/lsu.sv    |  2 +-
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/pipelined/src/lsu/atomic.sv b/pipelined/src/lsu/atomic.sv
index 64c1dc4b..69591928 100644
--- a/pipelined/src/lsu/atomic.sv
+++ b/pipelined/src/lsu/atomic.sv
@@ -1,10 +1,13 @@
 ///////////////////////////////////////////
 // atomic.sv
 //
-// Written: Ross Thompson ross1728@gmail.com January 31, 2022
-// Modified:
+// Written: Ross Thompson ross1728@gmail.com
+// Created: 31 January 2022
+// Modified: 18 January 2023
 //
-// Purpose: atomic data path.
+// Purpose: Wrapper for amoalu and lrsc
+//
+// Documentation: RISC-V System on Chip Design Chapter 14 (Figure ***)
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
@@ -28,18 +31,19 @@
 
 module atomic (
   input logic                clk,
-  input logic                reset, StallW,
-  input logic [`XLEN-1:0]    ReadDataM,
-  input logic [`XLEN-1:0]    IHWriteDataM, 
-  input logic [`PA_BITS-1:0] PAdrM,
-  input logic [6:0]          LSUFunct7M,
-  input logic [2:0]          LSUFunct3M,
-  input logic [1:0]          LSUAtomicM,
-  input logic [1:0]          PreLSURWM,
-  input logic                IgnoreRequest,
-  output logic [`XLEN-1:0]   IMAWriteDataM,
-  output logic               SquashSCW,
-  output logic [1:0]         LSURWM
+  input logic                reset, 
+  input logic                StallW,
+  input logic [`XLEN-1:0]    ReadDataM,      // LSU ReadData XLEN because FPU does not issue atomic memory operation from FPU registers
+  input logic [`XLEN-1:0]    IHWriteDataM,   // LSU WriteData XLEN because FPU does not issue atomic memory operation from FPU registers
+  input logic [`PA_BITS-1:0] PAdrM,          // Physical memory address
+  input logic [6:0]          LSUFunct7M,     // AMO alu operation gated by HPTW
+  input logic [2:0]          LSUFunct3M,     // IEU or HPTW memory operation size
+  input logic [1:0]          LSUAtomicM,     // 10: AMO operation, select AMOResult as the writedata output, 01: LR/SC operation
+  input logic [1:0]          PreLSURWM,      // IEU or HPTW Read/Write signal
+  input logic                IgnoreRequest,  // On FlushM or TLB miss ignore memory operation
+  output logic [`XLEN-1:0]   IMAWriteDataM,  // IEU, HPTW, or AMO write data
+  output logic               SquashSCW,      // Store conditional failed disable write to GPR
+  output logic [1:0]         LSURWM          // IEU or HPTW Read/Write signal gated by LR/SC
 );
 
   logic [`XLEN-1:0]          AMOResult;
diff --git a/pipelined/src/lsu/lsu.sv b/pipelined/src/lsu/lsu.sv
index 95f058c3..b0998510 100644
--- a/pipelined/src/lsu/lsu.sv
+++ b/pipelined/src/lsu/lsu.sv
@@ -131,7 +131,7 @@ module lsu (
   logic                     LSULoadAccessFaultM;                     // Load acces fault
   logic 					LSUStoreAmoAccessFaultM;                 // Store access fault
   logic                     IgnoreRequestTLB;                        // On either ITLB or DTLB miss, ignore miss so HPTW can handle
-  logic 					IgnoreRequest;                           // On FlushM, ignore TLB miss
+  logic 					IgnoreRequest;                           // On FlushM or TLB miss ignore memory operation
   logic                     SelDTIM;                                 // Select DTIM rather than bus or D$
 
   

From 2048edb7a0a8949334c88bf759d6de973e3d36fc Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:13:18 -0600
Subject: [PATCH 10/24] Renamed signals in amoalu.

---
 pipelined/src/lsu/amoalu.sv | 32 ++++++++++++++++----------------
 pipelined/src/lsu/atomic.sv |  3 +--
 2 files changed, 17 insertions(+), 18 deletions(-)

diff --git a/pipelined/src/lsu/amoalu.sv b/pipelined/src/lsu/amoalu.sv
index 46d5e219..eda3576b 100644
--- a/pipelined/src/lsu/amoalu.sv
+++ b/pipelined/src/lsu/amoalu.sv
@@ -30,11 +30,11 @@
 `include "wally-config.vh"
 
 module amoalu (
-  input  logic [`XLEN-1:0] srca,  // LSU's ReadData *** may want to change signal names.
-  input  logic [`XLEN-1:0] srcb,  // LSU's WriteData
-  input  logic [6:0]       funct, // ALU Operation
-  input  logic [1:0]       width, // Memoy access width
-  output logic [`XLEN-1:0] result // ALU output
+  input  logic [`XLEN-1:0] ReadDataM,    // LSU's ReadData
+  input  logic [`XLEN-1:0] IHWriteDataM, // LSU's WriteData
+  input  logic [6:0]       LSUFunct7M,   // ALU Operation
+  input  logic [2:0]       LSUFunct3M,   // Memoy access width
+  output logic [`XLEN-1:0] AMOResult     // ALU output
 );
 
   logic [`XLEN-1:0] a, b, y;
@@ -43,7 +43,7 @@ module amoalu (
   // a single carry chain should be shared for + and the four min/max
   // and the same mux can be used to select b for swap.
   always_comb 
-    case (funct[6:2])
+    case (LSUFunct7M[6:2])
       5'b00001: y = b;                                      // amoswap
       5'b00000: y = a + b;                                  // amoadd
       5'b00100: y = a ^ b;                                  // amoxor
@@ -58,19 +58,19 @@ module amoalu (
 
   // sign extend if necessary
   if (`XLEN == 32) begin:sext
-    assign a = srca;
-    assign b = srcb;
-    assign result = y;
+    assign a = ReadDataM;
+    assign b = IHWriteDataM;
+    assign AMOResult = y;
   end else begin:sext // `XLEN = 64
     always_comb 
-      if (width == 2'b10) begin // sign-extend word-length operations
-        a = {{32{srca[31]}}, srca[31:0]};
-        b = {{32{srcb[31]}}, srcb[31:0]};
-        result = {{32{y[31]}}, y[31:0]};
+      if (LSUFunct3M[1:0] == 2'b10) begin // sign-extend word-length operations
+        a = {{32{ReadDataM[31]}}, ReadDataM[31:0]};
+        b = {{32{IHWriteDataM[31]}}, IHWriteDataM[31:0]};
+        AMOResult = {{32{y[31]}}, y[31:0]};
       end else begin
-        a = srca;
-        b = srcb;
-        result = y;
+        a = ReadDataM;
+        b = IHWriteDataM;
+        AMOResult = y;
       end
   end
 endmodule
diff --git a/pipelined/src/lsu/atomic.sv b/pipelined/src/lsu/atomic.sv
index 69591928..fc9ede11 100644
--- a/pipelined/src/lsu/atomic.sv
+++ b/pipelined/src/lsu/atomic.sv
@@ -49,8 +49,7 @@ module atomic (
   logic [`XLEN-1:0]          AMOResult;
   logic                      MemReadM;
 
-  amoalu amoalu(.srca(ReadDataM), .srcb(IHWriteDataM), .funct(LSUFunct7M), .width(LSUFunct3M[1:0]), 
-                .result(AMOResult));
+  amoalu amoalu(.ReadDataM, .IHWriteDataM, .LSUFunct7M, .LSUFunct3M, .AMOResult);
 
   mux2 #(`XLEN) wdmux(IHWriteDataM, AMOResult, LSUAtomicM[1], IMAWriteDataM);
   assign MemReadM = PreLSURWM[1] & ~IgnoreRequest;

From 22eee73a45f005e78848e500278e27dd28fae24b Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:16:20 -0600
Subject: [PATCH 11/24] Formatting.

---
 pipelined/src/lsu/dtim.sv | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/pipelined/src/lsu/dtim.sv b/pipelined/src/lsu/dtim.sv
index a5f74e91..c4288d7a 100644
--- a/pipelined/src/lsu/dtim.sv
+++ b/pipelined/src/lsu/dtim.sv
@@ -1,10 +1,14 @@
 ///////////////////////////////////////////
 // dtim.sv
 //
-// Written: Ross Thompson ross1728@gmail.com January 30, 2022
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com 
+// Created: 30 January 2022
+// Modified: 18 January 2023
+//
+// Purpose: tightly integrated memory into the LSU.
+//
+// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.12)
 //
-// Purpose: simple memory with bus or cache.
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
@@ -27,10 +31,10 @@
 
 module dtim(
   input logic 				 clk, 
-  input logic 				 ce,            // Chip Enable
+  input logic 				 FlushW,        
+  input logic 				 ce,            // Chip Enable.  0: Holds ReadDataWordM
   input logic [1:0] 		 MemRWM,        // Read/Write control
   input logic [`PA_BITS-1:0] AdrM,          // Execution stage memory address
-  input logic 				 FlushW, 
   input logic [`LLEN-1:0] 	 WriteDataM,    // Write data from IEU
   input logic [`LLEN/8-1:0]  ByteMaskM,     // Selects which bytes within a word to write
   output logic [`LLEN-1:0] 	 ReadDataWordM  // Read data before subword selection

From cbf46f417a5bfc9a8c9ad1ac59732ca2520ba5b9 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:16:56 -0600
Subject: [PATCH 12/24] Formatting.

---
 pipelined/src/lsu/endianswap.sv | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pipelined/src/lsu/endianswap.sv b/pipelined/src/lsu/endianswap.sv
index e1fa1963..97846d97 100644
--- a/pipelined/src/lsu/endianswap.sv
+++ b/pipelined/src/lsu/endianswap.sv
@@ -1,8 +1,9 @@
 ///////////////////////////////////////////
 // endianswap.sv
 //
-// Written: David_Harris@hmc.edu 7 May 2022
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 7 May 2022
+// Modified: 18 January 2023
 //
 // Purpose: Swap byte order for Big-Endian accesses
 // 

From 469efa61afce6f41b06bf101e6967b3e40e1bced Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:17:48 -0600
Subject: [PATCH 13/24] Formatting.

---
 pipelined/src/lsu/lrsc.sv | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/pipelined/src/lsu/lrsc.sv b/pipelined/src/lsu/lrsc.sv
index 80b584dc..7edae6b8 100644
--- a/pipelined/src/lsu/lrsc.sv
+++ b/pipelined/src/lsu/lrsc.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // lrsc.sv
 //
-// Written: David_Harris@hmc.edu 17 July 2021
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 17 July 2021
+// Modified: 18 January 2023
 //
 // Purpose: Load Reserved / Store Conditional unit
 //          Track the reservation and squash the store if it fails
+//
+// Documentation: RISC-V System on Chip Design Chapter 14 (Figure ***)
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 

From fb234d506de9ab6faa1e4ae109edf8b62b945c5f Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:20:22 -0600
Subject: [PATCH 14/24] Formatted subword* and bytemask.

---
 pipelined/src/lsu/subwordread.sv  | 7 +++++--
 pipelined/src/lsu/subwordwrite.sv | 7 +++++--
 pipelined/src/lsu/swbytemask.sv   | 7 +++++--
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/pipelined/src/lsu/subwordread.sv b/pipelined/src/lsu/subwordread.sv
index ade4d3d4..784db694 100644
--- a/pipelined/src/lsu/subwordread.sv
+++ b/pipelined/src/lsu/subwordread.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // subwordread.sv
 //
-// Written: David_Harris@hmc.edu 9 January 2021
-// Modified: 
+// Written: David_Harris@hmc.edu 
+// Created: 9 January 2021
+// Modified: 18 January 2023 
 //
 // Purpose: Extract subwords and sign extend for reads
 // 
+// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.9)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
diff --git a/pipelined/src/lsu/subwordwrite.sv b/pipelined/src/lsu/subwordwrite.sv
index ae18b840..ee26b78f 100644
--- a/pipelined/src/lsu/subwordwrite.sv
+++ b/pipelined/src/lsu/subwordwrite.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // subwordwrite.sv
 //
-// Written: David_Harris@hmc.edu 9 January 2021
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 9 January 2021
+// Modified: 18 January 2023 
 //
 // Purpose: Masking and muxing for subword writes
 // 
+// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.9)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
diff --git a/pipelined/src/lsu/swbytemask.sv b/pipelined/src/lsu/swbytemask.sv
index 6167e4ea..17eedd4c 100644
--- a/pipelined/src/lsu/swbytemask.sv
+++ b/pipelined/src/lsu/swbytemask.sv
@@ -1,11 +1,14 @@
 ///////////////////////////////////////////
 // swbytemask.sv
 //
-// Written: David_Harris@hmc.edu 9 January 2021
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 9 January 2021
+// Modified: 18 January 2023
 //
 // Purpose: On-chip RAM, external to core
 // 
+// Documentation: RISC-V System on Chip Design Chapter 4 (Figure 4.9)
+//
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
 // Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University

From 997dda11a8ffbb4b3fd4edb699845d9f9ac2da80 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:26:51 -0600
Subject: [PATCH 15/24] Added comments to decompress.sv. May want to consider
 additional documentation.

---
 pipelined/src/ifu/decompress.sv | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/pipelined/src/ifu/decompress.sv b/pipelined/src/ifu/decompress.sv
index aec215f6..190ff77f 100644
--- a/pipelined/src/ifu/decompress.sv
+++ b/pipelined/src/ifu/decompress.sv
@@ -1,10 +1,15 @@
 ///////////////////////////////////////////
 // decompress.sv
 //
-// Written: David_Harris@hmc.edu 9 January 2021
-// Modified: 
+// Written: David_Harris@hmc.edu
+// Created: 9 January 2021
+// Modified: 18 January 2023
 //
 // Purpose: Expand 16-bit compressed instructions to 32 bits
+//
+// Documentation: RISC-V System on Chip Design Chapter 11 (Section 11.3.1)
+//                RISC-V Specification 13 Dec 2019 Chapter 16 pg. 97
+// *** probably need more documentation in this file since the book is very light on decompression.
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
@@ -27,9 +32,10 @@
 `include "wally-config.vh"
 
 module decompress (
-  input  logic [31:0] InstrRawD,
-  output logic [31:0] InstrD,
-  output logic        IllegalCompInstrD);
+  input  logic [31:0] InstrRawD,         // 32-bit instruction or raw un decompress instruction
+  output logic [31:0] InstrD,            // Decompressed instruction
+  output logic        IllegalCompInstrD  // Invalid decompressed instruction
+);
                         
   logic [15:0]        instr16;
   logic [4:0]         rds1, rs2, rs1p, rs2p, rds1p, rdp;

From 19e4d0f7cda3222e9179ad81ed8011877691fa2c Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:44:30 -0600
Subject: [PATCH 16/24] Cleanup dtim and irom.

---
 pipelined/src/ifu/ifu.sv  |  6 ++++--
 pipelined/src/ifu/irom.sv | 15 ++++++++-------
 pipelined/src/lsu/dtim.sv |  4 ++--
 pipelined/src/lsu/lsu.sv  |  2 +-
 4 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/pipelined/src/ifu/ifu.sv b/pipelined/src/ifu/ifu.sv
index c0d8837d..c65fe0e8 100644
--- a/pipelined/src/ifu/ifu.sv
+++ b/pipelined/src/ifu/ifu.sv
@@ -189,9 +189,11 @@ module ifu (
   assign IgnoreRequest = ITLBMissF | FlushD;
 
   // The IROM uses untranslated addresses, so it is not compatible with virtual memory.
-  if (`IROM_SUPPORTED) begin : irom 
+  if (`IROM_SUPPORTED) begin : irom
+	logic IROMce;
+	assign IROMce = ~GatedStallD | reset;
     assign IFURWF = 2'b10;
-    irom irom(.clk, .ce(~GatedStallD | reset), .Adr(PCNextFSpill[`XLEN-1:0]), .ReadData(IROMInstrF));
+    irom irom(.clk, .ce(IROMce), .Adr(PCNextFSpill[`XLEN-1:0]), .IROMInstrF);
   end else begin
     assign IFURWF = 2'b10;
   end
diff --git a/pipelined/src/ifu/irom.sv b/pipelined/src/ifu/irom.sv
index 3e7e4633..74adfb8e 100644
--- a/pipelined/src/ifu/irom.sv
+++ b/pipelined/src/ifu/irom.sv
@@ -26,23 +26,24 @@
 `include "wally-config.vh"
 
 module irom(
-  input logic               clk, ce,
-  input logic [`XLEN-1:0]   Adr,
-  output logic [31:0]  ReadData
+  input logic 			  clk, 
+  input logic 			  ce,        // Chip Enable.  0: Holds IROMInstrF constant
+  input logic [`XLEN-1:0] Adr,       // PCNextFSpill
+  output logic [31:0] 	  IROMInstrF // Instruction read data
 );
 
   localparam ADDR_WDITH = $clog2(`IROM_RANGE/8); 
   localparam OFFSET = $clog2(`XLEN/8);
 
-  logic [`XLEN-1:0] ReadDataFull;
+  logic [`XLEN-1:0] IROMInstrFFull;
 
-  rom1p1r #(ADDR_WDITH, `XLEN) rom(.clk, .ce, .addr(Adr[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(ReadDataFull));
-  if (`XLEN == 32) assign ReadData = ReadDataFull;
+  rom1p1r #(ADDR_WDITH, `XLEN) rom(.clk, .ce, .addr(Adr[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(IROMInstrFFull));
+  if (`XLEN == 32) assign IROMInstrF = IROMInstrFFull;
   // have to delay Ardr[OFFSET-1] by 1 cycle
   else             begin
     logic AdrD;
     flopen #(1) AdrReg(clk, ce, Adr[OFFSET-1], AdrD);
-    assign ReadData = AdrD ? ReadDataFull[63:32] : ReadDataFull[31:0];
+    assign IROMInstrF = AdrD ? IROMInstrFFull[63:32] : IROMInstrFFull[31:0];
   end
 endmodule  
   
diff --git a/pipelined/src/lsu/dtim.sv b/pipelined/src/lsu/dtim.sv
index c4288d7a..4a5cba1f 100644
--- a/pipelined/src/lsu/dtim.sv
+++ b/pipelined/src/lsu/dtim.sv
@@ -34,7 +34,7 @@ module dtim(
   input logic 				 FlushW,        
   input logic 				 ce,            // Chip Enable.  0: Holds ReadDataWordM
   input logic [1:0] 		 MemRWM,        // Read/Write control
-  input logic [`PA_BITS-1:0] AdrM,          // Execution stage memory address
+  input logic [`PA_BITS-1:0] DTIMAdr,       // No stall: Execution stage memory address. Stall: Memory stage memory address
   input logic [`LLEN-1:0] 	 WriteDataM,    // Write data from IEU
   input logic [`LLEN/8-1:0]  ByteMaskM,     // Selects which bytes within a word to write
   output logic [`LLEN-1:0] 	 ReadDataWordM  // Read data before subword selection
@@ -48,6 +48,6 @@ module dtim(
   assign we = MemRWM[0]  & ~FlushW;  // have to ignore write if Trap.
 
   ram1p1rwbe #(.DEPTH(`DTIM_RANGE/8), .WIDTH(`LLEN)) 
-    ram(.clk, .ce, .we, .bwe(ByteMaskM), .addr(AdrM[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(ReadDataWordM), .din(WriteDataM));
+    ram(.clk, .ce, .we, .bwe(ByteMaskM), .addr(DTIMAdr[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(ReadDataWordM), .din(WriteDataM));
 endmodule  
   
diff --git a/pipelined/src/lsu/lsu.sv b/pipelined/src/lsu/lsu.sv
index b0998510..6d958d02 100644
--- a/pipelined/src/lsu/lsu.sv
+++ b/pipelined/src/lsu/lsu.sv
@@ -232,7 +232,7 @@ module lsu (
     // **** fix ReadDataWordM to be LLEN. ByteMask is wrong length.
     // **** create config to support DTIM with floating point.
     dtim dtim(.clk, .ce(~GatedStallW), .MemRWM(DTIMMemRWM),
-              .AdrM(DTIMAdr), .FlushW, .WriteDataM(LSUWriteDataM), 
+              .DTIMAdr, .FlushW, .WriteDataM(LSUWriteDataM), 
               .ReadDataWordM(DTIMReadDataWordM[`XLEN-1:0]), .ByteMaskM(ByteMaskM[`XLEN/8-1:0]));
   end else begin
   end

From 026d09b79bf4313bd62c7e81118e47d16514254b Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 18:47:02 -0600
Subject: [PATCH 17/24] More IROM cleanup.

---
 pipelined/src/ifu/irom.sv | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pipelined/src/ifu/irom.sv b/pipelined/src/ifu/irom.sv
index 74adfb8e..818384b9 100644
--- a/pipelined/src/ifu/irom.sv
+++ b/pipelined/src/ifu/irom.sv
@@ -39,8 +39,9 @@ module irom(
 
   rom1p1r #(ADDR_WDITH, `XLEN) rom(.clk, .ce, .addr(Adr[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(IROMInstrFFull));
   if (`XLEN == 32) assign IROMInstrF = IROMInstrFFull;
-  // have to delay Ardr[OFFSET-1] by 1 cycle
   else             begin
+	// IROM is aligned to XLEN words, but instructions are 32 bits.  Select between the two
+	// haves.  Adr is the Next PCF not PCF so we delay 1 cycle.
     logic AdrD;
     flopen #(1) AdrReg(clk, ce, Adr[OFFSET-1], AdrD);
     assign IROMInstrF = AdrD ? IROMInstrFFull[63:32] : IROMInstrFFull[31:0];

From 7289fa8d44c5792f8879671195563923a3a99b84 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 19:10:34 -0600
Subject: [PATCH 18/24] Reduced complexity of spill logic by ensuring the irom
 outputs offset instrutions on a spill.

---
 pipelined/src/ifu/irom.sv         | 13 +++++++++----
 pipelined/src/ifu/spillsupport.sv |  5 ++---
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/pipelined/src/ifu/irom.sv b/pipelined/src/ifu/irom.sv
index 818384b9..52c9d97b 100644
--- a/pipelined/src/ifu/irom.sv
+++ b/pipelined/src/ifu/irom.sv
@@ -36,15 +36,20 @@ module irom(
   localparam OFFSET = $clog2(`XLEN/8);
 
   logic [`XLEN-1:0] IROMInstrFFull;
+  logic [31:0] 		RawIROMInstrF;
+
+  logic [1:0] 			AdrD;
+  flopen #(2) AdrReg(clk, ce, Adr[2:1], AdrD);
 
   rom1p1r #(ADDR_WDITH, `XLEN) rom(.clk, .ce, .addr(Adr[ADDR_WDITH+OFFSET-1:OFFSET]), .dout(IROMInstrFFull));
-  if (`XLEN == 32) assign IROMInstrF = IROMInstrFFull;
+  if (`XLEN == 32) assign RawIROMInstrF = IROMInstrFFull;
   else             begin
 	// IROM is aligned to XLEN words, but instructions are 32 bits.  Select between the two
 	// haves.  Adr is the Next PCF not PCF so we delay 1 cycle.
-    logic AdrD;
-    flopen #(1) AdrReg(clk, ce, Adr[OFFSET-1], AdrD);
-    assign IROMInstrF = AdrD ? IROMInstrFFull[63:32] : IROMInstrFFull[31:0];
+    assign RawIROMInstrF = AdrD[1] ? IROMInstrFFull[63:32] : IROMInstrFFull[31:0];
   end
+  // If the memory addres is aligned to 2 bytes return the upper 2 bytes in the lower 2 bytes.
+  // The spill logic will handle merging the two together.
+  assign IROMInstrF = AdrD[0] ? {16'b0, RawIROMInstrF[31:16]} : RawIROMInstrF;
 endmodule  
   
diff --git a/pipelined/src/ifu/spillsupport.sv b/pipelined/src/ifu/spillsupport.sv
index 3cf6ea94..4cb6e359 100644
--- a/pipelined/src/ifu/spillsupport.sv
+++ b/pipelined/src/ifu/spillsupport.sv
@@ -51,7 +51,7 @@ module spillsupport #(parameter CACHE_ENABLED)
   logic                TakeSpillF;
   logic                SpillF;
   logic                SelSpillF, SpillSaveF;
-  logic [15:0]         SpillDataLine0, SavedInstr;
+  logic [15:0]         SpillDataLine0;
   typedef enum logic [1:0]     {STATE_READY, STATE_SPILL} statetype;
   (* mark_debug = "true" *)  statetype CurrState, NextState;
 
@@ -83,12 +83,11 @@ module spillsupport #(parameter CACHE_ENABLED)
   assign SelNextSpillF = (CurrState == STATE_READY & TakeSpillF) |
                          (CurrState == STATE_SPILL & IFUCacheBusStallD);
   assign SpillSaveF = (CurrState == STATE_READY) & TakeSpillF;
-  assign SavedInstr = CACHE_ENABLED ? InstrRawF[15:0] : InstrRawF[31:16];
   
   flopenr #(16) SpillInstrReg(.clk(clk),
                               .en(SpillSaveF  & ~Flush),
                               .reset(reset),
-                              .d(SavedInstr),
+                              .d(InstrRawF[15:0]),
                               .q(SpillDataLine0));
 
   mux2 #(32) postspillmux(.d0(InstrRawF), .d1({InstrRawF[15:0], SpillDataLine0}), .s(SpillF),

From cd2f7c6208c696ae69a4e4967e23dcc6c5c65662 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 19:11:30 -0600
Subject: [PATCH 19/24] Formatting.

---
 pipelined/src/ifu/irom.sv | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pipelined/src/ifu/irom.sv b/pipelined/src/ifu/irom.sv
index 52c9d97b..ba23cf23 100644
--- a/pipelined/src/ifu/irom.sv
+++ b/pipelined/src/ifu/irom.sv
@@ -1,8 +1,9 @@
 ///////////////////////////////////////////
 // irom.sv
 //
-// Written: Ross Thompson ross1728@gmail.com January 30, 2022
-// Modified: 
+// Written: Ross Thompson ross1728@gmail.com
+// Created: 30 January 2022
+// Modified: 18 January 2023
 //
 // Purpose: simple instruction ROM
 // A component of the CORE-V-WALLY configurable RISC-V project.

From 49daa736b12cb7719b77cb17b2fa97627d295090 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 19:25:54 -0600
Subject: [PATCH 20/24] Formatting spillsupport.

---
 pipelined/src/ifu/ifu.sv          |  5 ++-
 pipelined/src/ifu/spillsupport.sv | 58 ++++++++++++++++---------------
 2 files changed, 32 insertions(+), 31 deletions(-)

diff --git a/pipelined/src/ifu/ifu.sv b/pipelined/src/ifu/ifu.sv
index c65fe0e8..72967539 100644
--- a/pipelined/src/ifu/ifu.sv
+++ b/pipelined/src/ifu/ifu.sv
@@ -122,9 +122,8 @@ module ifu (
   /////////////////////////////////////////////////////////////////////////////////////////////
 
   if(`C_SUPPORTED) begin : SpillSupport
-    spillsupport #(`ICACHE) spillsupport(.clk, .reset, .StallF, .Flush(FlushD), .PCF, .PCPlus4F, .PCNextF, .InstrRawF(InstrRawF),
-      .InstrDAPageFaultF, .IFUCacheBusStallD, .ITLBMissF, .PCNextFSpill, .PCFSpill,
-      .SelNextSpillF, .PostSpillInstrRawF, .CompressedF);
+    spillsupport #(`ICACHE) spillsupport(.clk, .reset, .StallD, .FlushD, .PCF, .PCPlus4F, .PCNextF, .InstrRawF,
+      .InstrDAPageFaultF, .IFUCacheBusStallD, .ITLBMissF, .PCNextFSpill, .PCFSpill, .SelNextSpillF, .PostSpillInstrRawF, .CompressedF);
   end else begin : NoSpillSupport
     assign PCNextFSpill = PCNextF;
     assign PCFSpill = PCF;
diff --git a/pipelined/src/ifu/spillsupport.sv b/pipelined/src/ifu/spillsupport.sv
index 4cb6e359..89f86efc 100644
--- a/pipelined/src/ifu/spillsupport.sv
+++ b/pipelined/src/ifu/spillsupport.sv
@@ -28,37 +28,39 @@
 
 `include "wally-config.vh"
 
-module spillsupport #(parameter CACHE_ENABLED)
-  (input logic              clk,
-   input logic              reset,
-   input logic              StallF, Flush,
-   input logic [`XLEN-1:0]  PCF,
-   input logic [`XLEN-1:2]  PCPlus4F,
-   input logic [`XLEN-1:0]  PCNextF,
-   input logic [31:0]       InstrRawF,
-   input logic              IFUCacheBusStallD,
-   input logic              ITLBMissF, 
-   input logic              InstrDAPageFaultF, 
-   output logic [`XLEN-1:0] PCNextFSpill,
-   output logic [`XLEN-1:0] PCFSpill,
-   output logic             SelNextSpillF,
-   output logic [31:0]      PostSpillInstrRawF,
-   output logic             CompressedF);
+module spillsupport #(
+  parameter CACHE_ENABLED                     // Changes spill threshold to 1 if there is no cache
+)(input logic              clk,               
+  input logic 			   reset,
+  input logic 			   StallD, FlushD,
+  input logic [`XLEN-1:0]  PCF,               // 2 byte aligned PC in Fetch stage
+  input logic [`XLEN-1:2]  PCPlus4F,          // PCF + 4
+  input logic [`XLEN-1:0]  PCNextF,           // The next PCF
+  input logic [31:0] 	   InstrRawF,         // Instruction from the IROM, I$, or bus. Used to check if the instruction if compressed
+  input logic 			   IFUCacheBusStallD, // I$ or bus are stalled. Transition to second fetch of spill after the first is fetched
+  input logic 			   ITLBMissF,         // ITLB miss, ignore memory request
+  input logic 			   InstrDAPageFaultF, // Ignore memory request if the hptw support write and a DA page fault occurs (hptw is still active)
+  output logic [`XLEN-1:0] PCNextFSpill,      // The next PCF for one of the two memory addresses of the spill
+  output logic [`XLEN-1:0] PCFSpill,          // PCF for one of the two memory addresses of the spill
+  output logic 			   SelNextSpillF,     // During the transition between the two spill operations, the IFU should stall the pipeline
+  output logic [31:0] 	   PostSpillInstrRawF,// The final 32 bit instruction after merging the two spilled fetches into 1 instruction
+  output logic 			   CompressedF);      // The fetched instruction is compressed
 
-
-  localparam integer   SPILLTHRESHOLD = CACHE_ENABLED ? `ICACHE_LINELENINBITS/32 : 1;
-  logic [`XLEN-1:0]    PCPlus2F;
+  // Spill threshold occurs when all the cache offset PC bits are 1 (except [0]).  Without a cache this is just PCF[1]
+  localparam integer   SPILLTHRESHOLD = CACHE_ENABLED ? `ICACHE_LINELENINBITS/32 : 1; 
+  logic [`XLEN-1:0]    PCPlus2F;         
   logic                TakeSpillF;
   logic                SpillF;
-  logic                SelSpillF, SpillSaveF;
-  logic [15:0]         SpillDataLine0;
+  logic                SelSpillF;
+  logic 			   SpillSaveF;
+  logic [15:0]         InstrFirstHalf;
   typedef enum logic [1:0]     {STATE_READY, STATE_SPILL} statetype;
   (* mark_debug = "true" *)  statetype CurrState, NextState;
 
-  // compute PCF+2
+  // compute PCF+2 from the raw PC+4
   mux2 #(`XLEN) pcplus2mux(.d0({PCF[`XLEN-1:2], 2'b10}), .d1({PCPlus4F, 2'b00}), .s(PCF[1]), .y(PCPlus2F));
   // select between PCNextF and PCF+2
-  mux2 #(`XLEN) pcnextspillmux(.d0(PCNextF), .d1(PCPlus2F), .s(SelNextSpillF & ~Flush), .y(PCNextFSpill));
+  mux2 #(`XLEN) pcnextspillmux(.d0(PCNextF), .d1(PCPlus2F), .s(SelNextSpillF & ~FlushD), .y(PCNextFSpill));
   // select between PCF and PCF+2
   mux2 #(`XLEN) pcspillmux(.d0(PCF), .d1(PCPlus2F), .s(SelSpillF), .y(PCFSpill));
   
@@ -66,14 +68,14 @@ module spillsupport #(parameter CACHE_ENABLED)
   assign TakeSpillF = SpillF & ~IFUCacheBusStallD & ~(ITLBMissF | (`HPTW_WRITES_SUPPORTED & InstrDAPageFaultF));
   
   always_ff @(posedge clk)
-    if (reset | Flush)    CurrState <= #1 STATE_READY;
+    if (reset | FlushD)    CurrState <= #1 STATE_READY;
     else CurrState <= #1 NextState;
 
   always_comb begin
     case (CurrState)
       STATE_READY: if (TakeSpillF)                NextState = STATE_SPILL;
                    else                           NextState = STATE_READY;
-      STATE_SPILL: if(IFUCacheBusStallD | StallF) NextState = STATE_SPILL;
+      STATE_SPILL: if(IFUCacheBusStallD | StallD) NextState = STATE_SPILL;
                    else                           NextState = STATE_READY;
       default:                                    NextState = STATE_READY;
     endcase
@@ -85,12 +87,12 @@ module spillsupport #(parameter CACHE_ENABLED)
   assign SpillSaveF = (CurrState == STATE_READY) & TakeSpillF;
   
   flopenr #(16) SpillInstrReg(.clk(clk),
-                              .en(SpillSaveF  & ~Flush),
+                              .en(SpillSaveF  & ~FlushD),
                               .reset(reset),
                               .d(InstrRawF[15:0]),
-                              .q(SpillDataLine0));
+                              .q(InstrFirstHalf));
 
-  mux2 #(32) postspillmux(.d0(InstrRawF), .d1({InstrRawF[15:0], SpillDataLine0}), .s(SpillF),
+  mux2 #(32) postspillmux(.d0(InstrRawF), .d1({InstrRawF[15:0], InstrFirstHalf}), .s(SpillF),
     .y(PostSpillInstrRawF));
   assign CompressedF = PostSpillInstrRawF[1:0] != 2'b11;
 

From 47fdff6488b0b78e88464ca49b6e069cb3a52d55 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Wed, 18 Jan 2023 19:26:20 -0600
Subject: [PATCH 21/24] Formatting.

---
 pipelined/src/ifu/spillsupport.sv | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pipelined/src/ifu/spillsupport.sv b/pipelined/src/ifu/spillsupport.sv
index 89f86efc..51eaec1b 100644
--- a/pipelined/src/ifu/spillsupport.sv
+++ b/pipelined/src/ifu/spillsupport.sv
@@ -1,5 +1,5 @@
 ///////////////////////////////////////////
-// spillsupport.sv
+// spillsupport.sv *** rename to spill.sv
 //
 // Written: Ross Thompson ross1728@gmail.com January 28, 2022
 // Modified:

From e380fd71ffc0e95ba26ed0901feb3c65c19365fe Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Thu, 19 Jan 2023 14:08:42 -0600
Subject: [PATCH 22/24] Formatting and name changes.

---
 pipelined/src/ifu/ifu.sv                      |  6 ++--
 .../src/ifu/{spillsupport.sv => spill.sv}     | 36 ++++++++++++-------
 2 files changed, 26 insertions(+), 16 deletions(-)
 rename pipelined/src/ifu/{spillsupport.sv => spill.sv} (80%)

diff --git a/pipelined/src/ifu/ifu.sv b/pipelined/src/ifu/ifu.sv
index 72967539..8e89ceb0 100644
--- a/pipelined/src/ifu/ifu.sv
+++ b/pipelined/src/ifu/ifu.sv
@@ -121,10 +121,10 @@ module ifu (
   // Spill Support
   /////////////////////////////////////////////////////////////////////////////////////////////
 
-  if(`C_SUPPORTED) begin : SpillSupport
-    spillsupport #(`ICACHE) spillsupport(.clk, .reset, .StallD, .FlushD, .PCF, .PCPlus4F, .PCNextF, .InstrRawF,
+  if(`C_SUPPORTED) begin : Spill
+    spill #(`ICACHE) spill(.clk, .reset, .StallD, .FlushD, .PCF, .PCPlus4F, .PCNextF, .InstrRawF,
       .InstrDAPageFaultF, .IFUCacheBusStallD, .ITLBMissF, .PCNextFSpill, .PCFSpill, .SelNextSpillF, .PostSpillInstrRawF, .CompressedF);
-  end else begin : NoSpillSupport
+  end else begin : NoSpill
     assign PCNextFSpill = PCNextF;
     assign PCFSpill = PCF;
     assign PostSpillInstrRawF = InstrRawF;
diff --git a/pipelined/src/ifu/spillsupport.sv b/pipelined/src/ifu/spill.sv
similarity index 80%
rename from pipelined/src/ifu/spillsupport.sv
rename to pipelined/src/ifu/spill.sv
index 51eaec1b..f94be990 100644
--- a/pipelined/src/ifu/spillsupport.sv
+++ b/pipelined/src/ifu/spill.sv
@@ -1,5 +1,5 @@
 ///////////////////////////////////////////
-// spillsupport.sv *** rename to spill.sv
+// spill.sv
 //
 // Written: Ross Thompson ross1728@gmail.com January 28, 2022
 // Modified:
@@ -28,7 +28,7 @@
 
 `include "wally-config.vh"
 
-module spillsupport #(
+module spill #(
   parameter CACHE_ENABLED                     // Changes spill threshold to 1 if there is no cache
 )(input logic              clk,               
   input logic 			   reset,
@@ -57,13 +57,22 @@ module spillsupport #(
   typedef enum logic [1:0]     {STATE_READY, STATE_SPILL} statetype;
   (* mark_debug = "true" *)  statetype CurrState, NextState;
 
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // PC logic 
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  
   // compute PCF+2 from the raw PC+4
   mux2 #(`XLEN) pcplus2mux(.d0({PCF[`XLEN-1:2], 2'b10}), .d1({PCPlus4F, 2'b00}), .s(PCF[1]), .y(PCPlus2F));
   // select between PCNextF and PCF+2
   mux2 #(`XLEN) pcnextspillmux(.d0(PCNextF), .d1(PCPlus2F), .s(SelNextSpillF & ~FlushD), .y(PCNextFSpill));
   // select between PCF and PCF+2
   mux2 #(`XLEN) pcspillmux(.d0(PCF), .d1(PCPlus2F), .s(SelSpillF), .y(PCFSpill));
+
   
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // Detect spill
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+
   assign SpillF = &PCF[$clog2(SPILLTHRESHOLD)+1:1];
   assign TakeSpillF = SpillF & ~IFUCacheBusStallD & ~(ITLBMissF | (`HPTW_WRITES_SUPPORTED & InstrDAPageFaultF));
   
@@ -82,18 +91,19 @@ module spillsupport #(
   end
 
   assign SelSpillF = (CurrState == STATE_SPILL);
-  assign SelNextSpillF = (CurrState == STATE_READY & TakeSpillF) |
-                         (CurrState == STATE_SPILL & IFUCacheBusStallD);
-  assign SpillSaveF = (CurrState == STATE_READY) & TakeSpillF;
-  
-  flopenr #(16) SpillInstrReg(.clk(clk),
-                              .en(SpillSaveF  & ~FlushD),
-                              .reset(reset),
-                              .d(InstrRawF[15:0]),
-                              .q(InstrFirstHalf));
+  assign SelNextSpillF = (CurrState == STATE_READY & TakeSpillF) | (CurrState == STATE_SPILL & IFUCacheBusStallD);
+  assign SpillSaveF = (CurrState == STATE_READY) & TakeSpillF & ~FlushD;
+
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+  // Merge spilled instruction
+  ////////////////////////////////////////////////////////////////////////////////////////////////////
+
+  // save the first 2 bytes
+  flopenr #(16) SpillInstrReg(clk, reset, SpillSaveF, InstrRawF[15:0], InstrFirstHalf);
+
+  // merge together
+  mux2 #(32) postspillmux(InstrRawF, {InstrRawF[15:0], InstrFirstHalf}, SpillF, PostSpillInstrRawF);
 
-  mux2 #(32) postspillmux(.d0(InstrRawF), .d1({InstrRawF[15:0], InstrFirstHalf}), .s(SpillF),
-    .y(PostSpillInstrRawF));
   assign CompressedF = PostSpillInstrRawF[1:0] != 2'b11;
 
 endmodule

From ea96c2375f82c4c3408b49946b15538625635331 Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Thu, 19 Jan 2023 14:18:46 -0600
Subject: [PATCH 23/24] Formatting.

---
 pipelined/src/ifu/spill.sv | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pipelined/src/ifu/spill.sv b/pipelined/src/ifu/spill.sv
index f94be990..1cdcae98 100644
--- a/pipelined/src/ifu/spill.sv
+++ b/pipelined/src/ifu/spill.sv
@@ -7,6 +7,8 @@
 // Purpose: allows the IFU to make extra memory request if instruction address crosses
 //          cache line boundaries or if instruction address without a cache crosses
 //          XLEN/8 boundary.
+//
+// Documentation: RISC-V System on Chip Design Chapter 11 (Figure 11.5)
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 

From b027921902c89560b76eaa923bdc4f4a961738eb Mon Sep 17 00:00:00 2001
From: Ross Thompson <ross1728@gmail.com>
Date: Thu, 19 Jan 2023 15:06:37 -0600
Subject: [PATCH 24/24] Formatting.

---
 pipelined/src/ifu/bpred.sv | 48 ++++++++++++++++++--------------------
 pipelined/src/ifu/spill.sv |  5 ++--
 2 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/pipelined/src/ifu/bpred.sv b/pipelined/src/ifu/bpred.sv
index 219d9b4e..103e7d8c 100644
--- a/pipelined/src/ifu/bpred.sv
+++ b/pipelined/src/ifu/bpred.sv
@@ -1,13 +1,12 @@
 ///////////////////////////////////////////
 // bpred.sv
 //
-// Written: Ross Thomposn
-// Email: ross1728@gmail.com
-// Created: February 12, 2021
-// Modified: 
+// Written: Ross Thomposn ross1728@gmail.com
+// Created: 12 February 2021
+// Modified: 19 January 2023
 //
-// Purpose: Branch prediction unit
-//          Produces a branch prediction based on branch history.
+// Purpose: Branch direction prediction and jump/branch target prediction.
+//          Prediction made during the fetch stage and corrected in the execution stage.
 // 
 // A component of the CORE-V-WALLY configurable RISC-V project.
 // 
@@ -35,30 +34,29 @@ module bpred (
    input logic              FlushD, FlushE, FlushM, FlushW,
    // Fetch stage
    // the prediction
-   input logic [31:0]       InstrD,        // Decompressed decode stage instruction 
-   input logic [`XLEN-1:0]  PCNextF,       // Next Fetch Address
-   input logic [`XLEN-1:0]  PCPlus2or4F,   // PCF+2/4
-   output logic [`XLEN-1:0] PCNext1F,      // Branch Predictor predicted or corrected fetch address on miss prediction
-   output logic [`XLEN-1:0] NextValidPCE,  // Address of next valid instruction after the instruction in the Memory stage.
+   input logic [31:0]       InstrD,                    // Decompressed decode stage instruction. Used to decode instruction class
+   input logic [`XLEN-1:0]  PCNextF,                   // Next Fetch Address
+   input logic [`XLEN-1:0]  PCPlus2or4F,               // PCF+2/4
+   output logic [`XLEN-1:0] PCNext1F,                  // Branch Predictor predicted or corrected fetch address on miss prediction
+   output logic [`XLEN-1:0] NextValidPCE,              // Address of next valid instruction after the instruction in the Memory stage.
 
    // Update Predictor
-   input logic [`XLEN-1:0]  PCF,           // Fetch stage instruction address.
-   input logic [`XLEN-1:0]  PCD,           // Decode stage instruction address. Also the address the branch predictor took.
-   input logic [`XLEN-1:0]  PCE,           // Execution stage instruction address.
-   input logic [`XLEN-1:0]  PCM,           // Memory stage instruction address.
+   input logic [`XLEN-1:0]  PCF,                       // Fetch stage instruction address.
+   input logic [`XLEN-1:0]  PCD,                       // Decode stage instruction address. Also the address the branch predictor took.
+   input logic [`XLEN-1:0]  PCE,                       // Execution stage instruction address.
+   input logic [`XLEN-1:0]  PCM,                       // Memory stage instruction address.
 
-   // *** after reviewing the compressed instruction set I am leaning towards having the btb predict the instruction class.
-   // *** the specifics of how this is encode is subject to change.
-   input logic              PCSrcE,        // Executation stage branch is taken
-   input logic [`XLEN-1:0]  IEUAdrE,       // The branch/jump target address
-   input logic [`XLEN-1:0]  PCLinkE,       // The address following the branch instruction. (AKA Fall through address)
-   output logic [3:0]       InstrClassM,   // The valid instruction class. 1-hot encoded as jalr, ret, jr (not ret), j, br
+   // Branch and jump outcome
+   input logic              PCSrcE,                    // Executation stage branch is taken
+   input logic [`XLEN-1:0]  IEUAdrE,                   // The branch/jump target address
+   input logic [`XLEN-1:0]  PCLinkE,                   // The address following the branch instruction. (AKA Fall through address)
+   output logic [3:0]       InstrClassM,               // The valid instruction class. 1-hot encoded as jalr, ret, jr (not ret), j, br
 
    // Report branch prediction status
-   output logic             BPPredWrongE,  // Prediction is wrong.
-   output logic             DirPredictionWrongM, // Prediction direction is wrong.
-   output logic             BTBPredPCWrongM, // Prediction target wrong.
-   output logic             RASPredPCWrongM, // RAS prediction is wrong.
+   output logic             BPPredWrongE,              // Prediction is wrong.
+   output logic             DirPredictionWrongM,       // Prediction direction is wrong.
+   output logic             BTBPredPCWrongM,           // Prediction target wrong.
+   output logic             RASPredPCWrongM,           // RAS prediction is wrong.
    output logic             PredictionInstrClassWrongM // Class prediction is wrong.
    );
 
diff --git a/pipelined/src/ifu/spill.sv b/pipelined/src/ifu/spill.sv
index 1cdcae98..c1a1d8fa 100644
--- a/pipelined/src/ifu/spill.sv
+++ b/pipelined/src/ifu/spill.sv
@@ -1,8 +1,9 @@
 ///////////////////////////////////////////
 // spill.sv
 //
-// Written: Ross Thompson ross1728@gmail.com January 28, 2022
-// Modified:
+// Written: Ross Thompson ross1728@gmail.com
+// Created: 28 January 2022
+// Modified: 19 January 2023
 //
 // Purpose: allows the IFU to make extra memory request if instruction address crosses
 //          cache line boundaries or if instruction address without a cache crosses