forked from Github_Repos/cvw
115 lines
4.6 KiB
Systemverilog
115 lines
4.6 KiB
Systemverilog
///////////////////////////////////////////
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// subwordwrite.sv
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//
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// Written: David_Harris@hmc.edu 9 January 2021
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// Modified:
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//
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// Purpose: Masking and muxing for subword writes
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//
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// A component of the Wally configurable RISC-V project.
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//
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// Copyright (C) 2021 Harvey Mudd College & Oklahoma State University
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//
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// MIT LICENSE
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// Permission is hereby granted, free of charge, to any person obtaining a copy of this
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// software and associated documentation files (the "Software"), to deal in the Software
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// without restriction, including without limitation the rights to use, copy, modify, merge,
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// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
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// to whom the Software is furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all copies or
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// substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
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// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
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// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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// TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
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// OR OTHER DEALINGS IN THE SOFTWARE.
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////////////////////////////////////////////////////////////////////////////////////////////////
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`include "wally-config.vh"
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module subwordwrite (
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input logic [2:0] HADDRD,
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input logic [3:0] HSIZED,
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input logic [`XLEN-1:0] HWDATAIN,
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output logic [`XLEN-1:0] HWDATA,
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output logic [`XLEN/8-1:0] ByteWEN
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);
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logic [`XLEN-1:0] WriteDataSubwordDuplicated;
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if (`XLEN == 64) begin:sww
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logic [7:0] ByteMaskM;
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// Compute write mask
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assign ByteWEN = ByteMaskM;
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always_comb
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case(HSIZED[1:0])
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2'b00: begin ByteMaskM = 8'b00000000; ByteMaskM[HADDRD[2:0]] = 1; end // sb
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2'b01: case (HADDRD[2:1])
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2'b00: ByteMaskM = 8'b00000011;
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2'b01: ByteMaskM = 8'b00001100;
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2'b10: ByteMaskM = 8'b00110000;
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2'b11: ByteMaskM = 8'b11000000;
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endcase
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2'b10: if (HADDRD[2]) ByteMaskM = 8'b11110000;
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else ByteMaskM = 8'b00001111;
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2'b11: ByteMaskM = 8'b11111111;
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endcase
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// Handle subword writes
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always_comb
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case(HSIZED[1:0])
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2'b00: WriteDataSubwordDuplicated = {8{HWDATAIN[7:0]}}; // sb
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2'b01: WriteDataSubwordDuplicated = {4{HWDATAIN[15:0]}}; // sh
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2'b10: WriteDataSubwordDuplicated = {2{HWDATAIN[31:0]}}; // sw
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2'b11: WriteDataSubwordDuplicated = HWDATAIN; // sw
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endcase
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always_comb begin
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HWDATA='0;
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if (ByteMaskM[0]) HWDATA[7:0] = WriteDataSubwordDuplicated[7:0];
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if (ByteMaskM[1]) HWDATA[15:8] = WriteDataSubwordDuplicated[15:8];
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if (ByteMaskM[2]) HWDATA[23:16] = WriteDataSubwordDuplicated[23:16];
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if (ByteMaskM[3]) HWDATA[31:24] = WriteDataSubwordDuplicated[31:24];
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if (ByteMaskM[4]) HWDATA[39:32] = WriteDataSubwordDuplicated[39:32];
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if (ByteMaskM[5]) HWDATA[47:40] = WriteDataSubwordDuplicated[47:40];
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if (ByteMaskM[6]) HWDATA[55:48] = WriteDataSubwordDuplicated[55:48];
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if (ByteMaskM[7]) HWDATA[63:56] = WriteDataSubwordDuplicated[63:56];
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end
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end else begin:sww // 32-bit
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logic [3:0] ByteMaskM;
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// Compute write mask
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assign ByteWEN = ByteMaskM;
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always_comb
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case(HSIZED[1:0])
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2'b00: begin ByteMaskM = 4'b0000; ByteMaskM[HADDRD[1:0]] = 1; end // sb
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2'b01: if (HADDRD[1]) ByteMaskM = 4'b1100;
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else ByteMaskM = 4'b0011;
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2'b10: ByteMaskM = 4'b1111;
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default: ByteMaskM = 4'b111; // shouldn't happen
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endcase
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// Handle subword writes
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always_comb
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case(HSIZED[1:0])
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2'b00: WriteDataSubwordDuplicated = {4{HWDATAIN[7:0]}}; // sb
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2'b01: WriteDataSubwordDuplicated = {2{HWDATAIN[15:0]}}; // sh
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2'b10: WriteDataSubwordDuplicated = HWDATAIN; // sw
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default: WriteDataSubwordDuplicated = HWDATAIN; // shouldn't happen
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endcase
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always_comb begin
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HWDATA='0;
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if (ByteMaskM[0]) HWDATA[7:0] = WriteDataSubwordDuplicated[7:0];
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if (ByteMaskM[1]) HWDATA[15:8] = WriteDataSubwordDuplicated[15:8];
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if (ByteMaskM[2]) HWDATA[23:16] = WriteDataSubwordDuplicated[23:16];
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if (ByteMaskM[3]) HWDATA[31:24] = WriteDataSubwordDuplicated[31:24];
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end
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end
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endmodule
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