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mips_mini.v
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`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date: 21:29:02 11/18/2018
// Design Name:
// Module Name: mip_16_mini
// Project Name:
// Target Devices:
// Tool versions:
// Description:
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
//////////////////////////////////////////////////////////////////////////////////
//--------------------------------------------------------------
//------------------------------------------------
// mipsmemsingle.v
// External memories used by MIPS single-cycle
//------------------------------------------------
module dmem(input clk, we,
input [15:0] a, wd,
output [15:0] rd);
reg [15:0] RAM[63:0];
assign rd = RAM[a[15:1]]; // word aligned
always @(posedge clk)
begin
if (we)
RAM[a[15:1]] <= wd;
end
endmodule
module imem(input [5 :0] a,
output [15:0] rd);
reg [15:0] RAM[10:0];
integer i;
initial
begin
RAM[0] = {3'd7, 3'd0, 3'd3, 7'd9};
RAM[2] = {3'd7, 3'd0, 3'd2, 7'd7};
RAM[4] = {3'd0, 3'd2, 3'd3, 3'd4, 4'd0};
RAM[6] = {3'd2, 13'd0};
// RAM[2] = {3'd7, 3'd3, 3'd7, -7'd9};
// RAM[3] = {3'd0, 3'd7, 3'd2, 3'd4, 4'd3};
// RAM[4] = {3'd0, 3'd3, 3'd4, 3'd5, 4'd2};
// RAM[5] = {3'd0, 3'd5, 3'd4, 3'd5, 4'd0};
// RAM[6] = {3'd6, 3'd5, 3'd7, 7'd10};
// RAM[7] = {3'd0, 3'd3, 3'd4, 3'd4, 4'd4};
// RAM[8] = {3'd6, 3'd4, 3'd0, 7'd1};
// RAM[9] = {3'd0, 3'd7, 3'd2, 3'd4, 4'd4};
// RAM[10] = {3'd7, 3'd0, 3'd5, 7'd0};
// RAM[11] = {3'd0, 3'd4, 3'd5, 3'd7, 4'd0};
// RAM[12] = {3'd5, 3'd3, 3'd7, 7'd30};
// RAM[13] = {3'd0, 3'd7, 3'd2, 3'd7, 4'd1};
// RAM[14] = {3'd4, 3'd0, 3'd2, 7'd42};
// RAM[15] = {3'd2, 13'd17};
// RAM[16] = {3'd7, 3'd0, 3'd2, 7'd1};
// RAM[17] = {3'd5, 3'd0, 3'd2, 7'd44};
// for (i = 3; i<63; i=i+1) RAM[i] = 0;
end
assign rd = RAM[a]; // word aligned
// $display("rd: %h", RAM[a]);
endmodule
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
//------------------------------------------------
// mipsparts.v
// Components used in MIPS processor
//------------------------------------------------
module alu(input [15:0] a, b,
input [2:0] alucont,
output reg [15:0] result,
output zero);
always@(*)
case(alucont)
3'b000: result <= a + b;
3'b001: result <= a - b;
3'b010: result <= a & b;
3'b011: result <= a | b;
3'b100: begin if(a < b) result <= 16'd1;
else result <= 16'd0;
end
default: result <= a + b;
endcase
assign zero = (result == 16'd0) ? 1'b1: 1'b0;
endmodule
module regfile(input clk,
input we3,
input [2:0] ra1, ra2, wa3,
input [15:0] wd3,
output [15:0] rd1, rd2);
reg [15:0] rf[15:0];
// three ported register file
// read two ports combinationally
// write third port on rising edge of clock
// register 0 hardwired to 0
always @(posedge clk)
if (we3) rf[wa3] <= wd3;
assign rd1 = (ra1 != 0) ? rf[ra1] : 0;
assign rd2 = (ra2 != 0) ? rf[ra2] : 0;
endmodule
module adder(input [15:0] a, b,
output [15:0] y);
assign y = a + b;
endmodule
module sl2(input [15:0] a,
output [15:0] y);
// shift left by 1
assign y = {a[14:0], 1'b0};
endmodule
module signext(input [6:0] a,
output [15:0] y);
assign y = {{9{a[6]}}, a};
endmodule
module flopr #(parameter WIDTH = 8)
(input clk, reset,
input [WIDTH-1:0] d,
output reg [WIDTH-1:0] q);
always @(posedge clk, posedge reset)
if (reset) q <= 0;
else q <= d;
endmodule
module flopenr #(parameter WIDTH = 8)
(input clk, reset,
input en,
input [WIDTH-1:0] d,
output reg [WIDTH-1:0] q);
always @(posedge clk, posedge reset)
if (reset) q <= 0;
else if (en) q <= d;
endmodule
module mux2 #(parameter WIDTH = 8)
(input [WIDTH-1:0] d0, d1,
input s,
output [WIDTH-1:0] y);
assign y = s ? d1 : d0;
endmodule
module mux4 #(parameter WIDTH = 8)
(input [WIDTH-1:0] d0, d1,
input [1:0] s,
output reg [WIDTH-1:0] y);
always @(d0 or d1 or s)
begin
case(s)
2'b00 : y <= d0;
2'b01 : y<= d1;
default : y<= WIDTH-1'dx;
endcase
end
endmodule
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
// single-cycle MIPS processor
module mips(input clk, reset,
output [15:0] pc,
input [15:0] instr,
output memwrite,
output [15:0] aluout, writedata,
input [15:0] readdata,
output [7:0] r);
wire [7:0] tmp;
wire [1:0] memtoreg, regdst;
wire branch,
pcsrc, zero,
alusrc, regwrite, jump;
wire [2:0] alucontrol;
assign r = aluout[7:0];
controller c(instr[15:13], instr[3:0], zero,
memtoreg[1:0], memwrite, pcsrc,
alusrc, regdst[1:0], regwrite, jump,
alucontrol);
datapath dp(clk, reset, memtoreg[1:0], pcsrc,
alusrc, regdst[1:0], regwrite, jump,
alucontrol,
zero, pc, instr,
aluout, writedata, readdata);
endmodule
module controller(input [2:0] op,
input [3:0] funct,
input zero,
output [1:0] memtoreg,
output memwrite,
output pcsrc, alusrc,
output [1:0] regdst,
output regwrite,
output jump,
output [2:0] alucontrol);
wire [1:0] aluop;
wire branch;
maindec md(op, memtoreg[1:0], memwrite, branch,
alusrc, regdst[1:0], regwrite, jump,
aluop);
aludec ad(funct, aluop, alucontrol);
assign pcsrc = branch & zero;
endmodule
module maindec(input [2:0] op,
output [1:0] memtoreg,
output memwrite,
output branch, alusrc,
output [1:0] regdst,
output regwrite,
output jump,
output [1:0] aluop);
reg [10:0] controls;
assign {regwrite, regdst[1:0], alusrc,
branch, memwrite,
memtoreg[1:0] , jump, aluop} = controls;
always @(*)
case(op)
3'b000: controls <= 11'b10100000000; //Rtype
3'b100: controls <= 11'b10010001011; //LW
3'b101: controls <= 11'b00010100011; //SW
3'b111: controls <= 11'b10010000011; //ADDI
3'b110: controls <= 11'b00001000001; //BEQ
3'b010: controls <= 11'b00000000100; //J
3'b011: controls <= 11'b11000010100; //Jal
3'b001: controls <= 11'b10010000010; //slti
default:controls <= 11'bxxxxxxxxxxx; //???
endcase
endmodule
module aludec(input [3:0] funct,
input [1:0] aluop,
output reg [2:0] alucontrol);
always @(*)
case(aluop)
2'b11: alucontrol <= 3'b000; // add
2'b01: alucontrol <= 3'b001; // sub
2'b10: alucontrol <= 3'b100; // slti
default: case(funct) // RTYPE
4'b0000: alucontrol <= 3'b000; // ADD
4'b0001: alucontrol <= 3'b001; // SUB
4'b0010: alucontrol <= 3'b010; // AND
4'b0011: alucontrol <= 3'b011; // OR
4'b0100: alucontrol <= 3'b100; // SLT
default: alucontrol <= 3'bxxx; // ???
endcase
endcase
endmodule
module datapath(input clk, reset,
input [1:0] memtoreg,
input pcsrc,
input alusrc,
input [1:0] regdst,
input regwrite, jump,
input [2:0] alucontrol,
output zero,
output [15:0] pc,
input [15:0] instr,
output [15:0] aluout, writedata,
input [15:0] readdata);
wire [2:0] writereg;
wire [15:0] pcnext, pcnextbr, pcplus2, pcbranch;
wire [15:0] signimm, signimmsh;
wire [15:0] srca, srcb;
wire [15:0] result;
//-------------------------------------------------------------------------------//
// next PC logic
flopr #(16) pcreg(clk, reset, pcnext, pc);
adder pcadd1(pc, 16'b10, pcplus2);
sl2 immsh(signimm, signimmsh);
adder pcadd2(pcplus2, signimmsh, pcbranch);
mux2 #(16) pcbrmux(pcplus2, pcbranch, pcsrc,
pcnextbr);
mux2 #(16) pcmux(pcnextbr, {pcplus2[15:14],
instr[12:0], 1'b0},
jump, pcnext);
// register file logic
regfile rf(clk, regwrite, instr[12:10],
instr[9:7], writereg,
result, srca, writedata);
mux4 #(3) wrmux(instr[9:7], instr[6:4],
regdst[1:0], writereg);
mux4 #(16) resmux(aluout, readdata,
memtoreg[1:0], result);
signext se(instr[6:0], signimm);
// ALU logic
mux2 #(16) srcbmux(writedata, signimm, alusrc,
srcb);
alu alu(srca, srcb, alucontrol,
aluout, zero);
endmodule
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
module rategen(
input clk,rst,
output cy
);
//Generate 1 clock wide pulse on output CY
reg [31:0] Q;
always @(posedge clk)
begin
if (rst | cy)
Q <= 0;
else
Q <= Q + 1;
end
assign cy = (Q == 100000000);
//assign cy = (Q == 4);
endmodule
//------------------------------------------------
// top.v
// Top level system including MIPS and memories
//------------------------------------------------
module top(input clk, reset,
output [15:0] writedata, dataadr,
output memwrite,
output [7:0] r);
rategen rg(clk, reset, cy);
wire [15:0] pc, instr, readdata;
// instantiate processor and memories
mips mips(cy, reset, pc, instr, memwrite, dataadr, writedata, readdata, r);
imem imem(pc[6:1], instr);
dmem dmem(cy, memwrite, dataadr, writedata, readdata);
endmodule