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made priority encoder parameterizable

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Kip Macsai-Goren 2021-05-28 18:09:28 -04:00
parent 0646e08609
commit 529226ac8d
1 changed files with 27 additions and 41 deletions
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68
wally-pipelined/src/mmu/priority_encoder.sv
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@ -4,7 +4,11 @@
// Written: tfleming@hmc.edu & jtorrey@hmc.edu 7 April 2021
// Based on implementation from https://www.allaboutcircuits.com/ip-cores/communication-controller/priority-encoder/
// *** Give proper LGPL attribution for above source
// Modified:
// Modified: Teo Ene 15 Apr 2021:
// Temporarily removed paramterized priority encoder for non-parameterized one
// To get synthesis working quickly
// Kmacsaigoren@hmc.edu 28 May 2021:
// Added working version of parameterized priority encoder.
//
// Purpose: One-hot encoding to binary encoder
//
@ -27,51 +31,33 @@
`include "wally-config.vh"
// Teo Ene 04/15:
// Temporarily removed paramterized priority encoder for non-parameterized one
// To get synthesis working quickly
module priority_encoder #(parameter BINARY_BITS = 3) (
input logic [7:0] one_hot,
output logic [2:0] binary
input logic [2**BINARY_BITS - 1:0] one_hot,
output logic [BINARY_BITS - 1:0] binary
);
// localparam ONE_HOT_BITS = 2**BINARY_BITS;
/*
genvar i, j;
generate
for (i = 0; i < ONE_HOT_BITS; i++) begin
for (j = 0; j < BINARY_BITS; j++) begin
if (i[j]) begin
assign binary[j] = one_hot[i];
end
end
end
endgenerate
*/
/*
logic [BINARY_BITS-1:0] binary_comb;
integer i;
always_comb begin
binary_comb = 0;
for (int i = 0; i < ONE_HOT_BITS; i++)
if (one_hot[i]) binary_comb = i;
binary = 0;
for (i = 0; i < 2**BINARY_BITS; i++) begin
if (one_hot[i]) binary = i; // prioritizes the most significant bit
end
end
// *** triple check synthesizability here
assign binary = binary_comb;
// Ideally this mimics the following:
/*
always_comb begin
casex (one_hot)
1xx ... x: binary = BINARY_BITS - 1;
01x ... x: binary = BINARY_BITS - 2;
001 ... x: binary = BINARY_BITS - 3;
{...}
00 ... 1xx: binary = 2;
00 ... 01x: binary = 1;
00 ... 001: binary = 0;
end
*/
always_comb
case (one_hot)
8'h1: binary=3'h0;
8'h2: binary=3'h1;
8'h4: binary=3'h2;
8'h8: binary=3'h3;
8'h10: binary=3'h4;
8'h20: binary=3'h5;
8'h40: binary=3'h6;
8'h80: binary=3'h7;
default: binary=3'h0; //should never happen
endcase
endmodule