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module fetch_stage (
input clk,
input en,
output reg ready,
input [15:0] addr_in,
output reg [15:0] instr_out,
output reg [15:0] pc_out
);
always @(posedge clk) begin
if(en) begin
ready <= 1'b1;
// sample proggy:
case(addr_in[15:1])
// 15'h0: instr_out <= 16'b0000_000_1_000_000_10; // xor r0,r0,r0
// 15'h1: instr_out <= 16'b0000_001_1_001_001_10; // xor r1,r1,r1
// 15'h2: instr_out <= 16'b0101_000_0_00010010; // mov rl0,$12
// 15'h3: instr_out <= 16'b0101_001_0_00110100; // mov rl1,$34
// 15'h4: instr_out <= 16'b0000_010_0_000_001_00; // add r2,r0,r1
// 15'h5: instr_out <= 16'b0000_011_0_001_000_01; // sub r3,r1,r0
// 15'h6: instr_out <= 16'b0100_000_0_011_00100; // mov r0,r3
// 15'h7: instr_out <= 16'b0000_100_1_100_100_10; // xor r4,r4,r4
// 15'h8: instr_out <= 16'b0111_00000_100_00000; // jmp r4
15'h0: instr_out <= 16'h0BB6;
15'h1: instr_out <= 16'h0102;
15'h2: instr_out <= 16'h0326;
15'h3: instr_out <= 16'h054A;
15'h4: instr_out <= 16'h5201;
15'h5: instr_out <= 16'h540A;
15'h6: instr_out <= 16'h0AA0;
15'h7: instr_out <= 16'h0004;
15'h8: instr_out <= 16'h0809;
15'h9: instr_out <= 16'h6AFA;
15'hA: instr_out <= 16'h6E00;
default: instr_out <= 16'b1111_000000000000; // nop
endcase
pc_out <= addr_in;
end
else begin
ready <= 1'b0;
end
end
endmodule
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