`define MIPS_PROG "uc.v" `define MEMBASE 'h400000 `define DATABASE 'h10010000 `define TEXTSIZE 'h100 `define MEMSIZE 'h200 `define MEMRANGE `MEMBASE:`MEMBASE+`MEMSIZE-1 `define A(addr) ((addr)-`DATABASE+`MEMBASE+`TEXTSIZE) `define MEM(addr) mem[((addr)-`DATABASE+`MEMBASE+`TEXTSIZE)] module proc(exc,clk); input clk; output exc; reg exc; reg [7:0] mem [`MEMRANGE]; reg [31:0] pc, npc, nnpc, ir; reg [31:0] gpr [0:31]; reg [5:0] opcode, funct; reg [4:0] rs, rt, rd, sa; reg [15:0] immed; reg [25:0] ii; reg [31:0] uimm16, simm16; reg [31:0] branch_target; // Values for funct field. parameter f_sll = 6'h0; parameter f_srl = 6'h2; parameter f_add = 6'h20; parameter f_sub = 6'h22; parameter f_or = 6'h25; // Values for opcode field. parameter o_j = 6'h2; parameter o_beq = 6'h4; parameter o_bne = 6'h5; parameter o_addi = 6'h8; parameter o_slti = 6'ha; parameter o_andi = 6'hc; parameter o_ori = 6'hd; parameter o_lui = 6'hf; parameter o_lw = 6'h23; parameter o_lbu = 6'h24; parameter o_sw = 6'h2b; parameter o_sb = 6'h28; initial begin exc = 0; pc = 0; npc = 4; end always @( posedge clk ) begin ir = {mem[pc],mem[pc+1],mem[pc+2],mem[pc+3]}; // R Format {opcode,rs,rt,rd,sa,funct} = ir; nnpc = npc + 4; // May be reassigned below. if( !opcode ) begin // // R-Format Instructions case( funct ) f_sll : gpr[rd] = gpr[rt] << sa; f_srl : gpr[rd] = gpr[rt] >> sa; f_add : gpr[rd] = gpr[rs] + gpr[rt]; f_or : gpr[rd] = gpr[rs] | gpr[rt]; f_sub : gpr[rd] = gpr[rs] - gpr[rt]; default : exc = 1; endcase end else begin // // I- and J-Format Instructions // I Format (Also uses opcode, rs, and rt.) immed = ir[15:0]; // J Format (Also uses opcode.) ii = ir[25:0]; uimm16 = { 16'b0, immed }; simm16 = immed[15] ? { 16'hffff, immed } : uimm16; branch_target = npc + ( simm16 << 2 ); case( opcode ) o_j : nnpc = {npc[31:28],ii,2'b0}; o_beq : if( gpr[rs] == gpr[rt] ) nnpc = branch_target; o_bne : if( gpr[rs] != gpr[rt] ) nnpc = branch_target; o_andi : gpr[rt] = gpr[rs] & uimm16; o_slti : gpr[rt] = gpr[rs] < simm16; o_addi : gpr[rt] = gpr[rs] + simm16; o_ori : gpr[rt] = gpr[rs] | uimm16; o_lui : gpr[rt] = { immed, 16'b0 }; o_lbu : gpr[rt] = { 24'b0, `MEM( gpr[rs] + simm16 ) }; o_sb : `MEM( gpr[rs] + simm16 ) = gpr[rt]; default : exc = 1; endcase end gpr[0] = 0; pc = npc; npc = nnpc; end endmodule `include "mipsi1tb.v"