57 lines
1.9 KiB
Systemverilog
57 lines
1.9 KiB
Systemverilog
// Create Date: 15:50:22 10/02/2019
|
|
// Design Name:
|
|
// Module Name: InstROM
|
|
// Project Name: CSE141L
|
|
// Tool versions:
|
|
// Description: Verilog module -- instruction ROM template
|
|
// preprogrammed with instruction values (see case statement)
|
|
//
|
|
// Revision: 2021.08.08
|
|
//
|
|
// A = program counter width
|
|
// W = machine code width -- do not change for CSE141L
|
|
module InstROM #(parameter A=12, W=9) (
|
|
input [A-1:0] InstAddress,
|
|
output logic[W-1:0] InstOut);
|
|
|
|
// (usually recommended) expression
|
|
// need $readmemh or $readmemb to initialize all of the elements
|
|
// This version will work best with assemblers, but you can try the alternative starting line 33
|
|
// This version is also by far the easiest if you have a long program scrip.
|
|
// declare 2-dimensional array, W bits wide, 2**A words deep
|
|
logic[W-1:0] inst_rom[2**A];
|
|
always_comb InstOut = inst_rom[InstAddress];
|
|
|
|
initial begin // load from external text file
|
|
$readmemb("machine_code.txt",inst_rom);
|
|
end
|
|
|
|
// Sample instruction format:
|
|
// {3bit opcode, 3bit rs or rt, 3bit rt, immediate, or branch target}
|
|
// then use LUT to map 3 bits to 10 for branch target, 8 for immediate
|
|
|
|
/* alternative to code shown below, which may be simpler -- either is fine
|
|
always_comb begin
|
|
InstOut = 'b0000000000; // default
|
|
case (InstAddress)
|
|
//opcode = 0 lhw, rs = 0, rt = 1
|
|
0 : InstOut = 'b0000000001; // load from address at reg 0 to reg 1
|
|
// opcode = 1 addi, rs/rt = 1, immediate = 1
|
|
|
|
1 : InstOut = 'b0001001001; // addi reg 1 and 1
|
|
|
|
// opcode = 2 shw, rs = 0, rt = 1
|
|
2 : InstOut = 'b0010000001; // sw reg 1 to address in reg 0
|
|
|
|
// opcode = 3 beqz, rs = 1, target = 1
|
|
3 : InstOut = 'b0011001001; // beqz reg1 to absolute address 1
|
|
|
|
// opcode = 15 halt
|
|
4 : InstOut = '1; // equiv to 10'b1111111111 or 'b1111111111 halt
|
|
// (default case already covered by opening statement)
|
|
endcase
|
|
end
|
|
*/
|
|
|
|
endmodule
|