Single cycle MIPS processor instruction execution - mips

Question

I am executing six instructions in this Single Cycle MIPS processor.
I am unable to figure error in ALU module.
Six instructions i am trying to execute are: Add, Sub, AND, OR, Load, Store
Right now, i am getting correct result for Addition only.
In five bit MUX, i have given an input 'a' and 'b'. How can i relate this input 'a' and 'b' to instruction source and detonation registers.
Also, how can i add 4 byte after the execution of each instruction (i.e. my program counter is unable to increment).
//ALU Block
module ALU (FunctField,ReadData1,out_inALU, ALUOp,ctr1,result);
input ALUOp;
input [5:0]FunctField;
input [31:0] ReadData1;
input [31:0] out_inALU;
output [2:0] ctr1;
reg [2:0] ctr1;
output [31:0] result;
reg [31:0] result;
always #(*)
begin
if(ALUOp == 1) //Arithmetic' Type Instructions
begin
case(FunctField)
//begin
6'b100000: ctr1 = 3'b010; //ADDITION in 'R' Type
6'b100010: ctr1 = 3'b110; // SUBTRACTION in 'R' Type
6'b100100: ctr1 = 3'b000; // AND in 'R' Type
6'b100101: ctr1 = 3'b001; // OR in 'R' Type
endcase
end
if(ALUOp == 0)
begin // LW/SW Type Instructions
if (ctr1 == 3'b010)
result = ReadData1 + out_inALU ;
else if (ctr1 == 3'b110)
result = ReadData1 - out_inALU ;
else if (ctr1 == 3'b000)
result = ReadData1 & out_inALU ;
else if (ctr1 == 3'b001)
result = ReadData1 | out_inALU;
end
result = ReadData1 | out_inALU ;
end
endmodule
// Data memory
module data_memory (ReadAddr, WriteAddr, WriteData1, clock,
MemWrite, MemRead,ReadData);
input [31:0] ReadAddr, WriteAddr, WriteData1;
input clock, MemWrite, MemRead;
reg [31:0] mem[0:50]; // For simulation this no. is enough
reg [31:0] i; // Temporary variable
output [31:0] ReadData;
reg [31:0] ReadData;
initial
begin
// Initial read-out
ReadData = 0;
// Initial memory content for testing purpose
for ( i = 0; i <= 50; i = i+1)
mem[i] = i;
end
// Memory content is always fetched with positive edge clock
always #(posedge clock)
begin
wait ( MemRead )
#10 ReadData = mem[ReadAddr];
wait ( MemWrite )
#10 mem[WriteAddr] = WriteData1;
end
endmodule
// Instruction Memory
module inst(addr,clock,instruction);
input clock;
input [ 31 : 0 ] addr;
output [ 31 : 0 ] instruction;
reg [ 31 : 0 ] instruction;
reg [ 31 : 0 ] MEM[0 :31 ] ;
initial
begin
MEM[ 0 ] <= 32'h10000011;
MEM[ 1 ] <= 32'h10000011 ;
MEM[ 2 ] <= 32'h20000022 ;
MEM[ 3 ] <= 32'h30000033 ;
MEM[ 4 ] <= 32'h40000044 ;
MEM[ 5 ] <= 32'h50000055 ;
MEM[ 6 ] <= 32'h60000066 ;
MEM[ 7 ] <= 32'h70000077 ;
MEM[ 8 ] <= 32'h80000088 ;
MEM[ 9 ] <= 32'h90000099 ;
end
always #( posedge clock )
begin
instruction <= MEM[ addr ] ;
end
endmodule
//Main module
module(reset, clock, regwrite,regDst,ALUSrc,MemtoReg,MemWrite,MemRead, input_PC)
input reset,clock;
input regWrite;
input regDst;
input ALUSrc;
input MemtoReg;
input MemWrite;
input MemRead;
input [31:0] input_PC;
wire [4:0] ReadReg1, ReadReg2, WriteReg;
wire [31:0] WriteData;
// Instantiation of modules
//Program Counter
wire [31:0] addr;
PC x1(input_PC,clock,reset,addr);
// Instruction Memory
wire [31:0] instruction;
inst x2(addr,clock,instruction);
//Multiplexer with regDst
reg[4:0] inputa,inputb;
MUX_2to1_5bit x3(inputa,inputb,regDst,WriteReg);
//Register File
wire [31:0] ReadData1,ReadData2;
Register_32 x4 ( ReadReg1, ReadReg2, WriteReg, WriteData, clock,
RegWrite,ReadData1, ReadData2);
//Sign Extender
wire [31:0] out_sign;
SignExtender_16to32 x5(immediate, out_sign);
//Multilpexer ALUSrc
wire [31:0] out_inALU;
MUX_2to1 x6( ReadData2 , out_sign, ALUSrc,out_inALU );
//ALU
wire [31:0] result;
wire [2:0] ctr1;
ALU x7 (FunctField,ReadData1,out_inALU, ALUOp,ctr1,result);
//Data Memory
reg [31:0] ReadAddr;
reg [31:0] WriteAddr;
wire [31:0] ReadData;
data_memory x8(ReadAddr, WriteAddr, WriteData, clock, MemWrite,
MemRead,ReadData);
//Multiplexer MemtoReg
MUX_2to1_memreg x9( result,ReadData,MemtoReg,WriteData);
endmodule
// Mux2 to 1_32 bit
module MUX_2to1( ReadData2 , outputData, ALUSrc,out_inALU );
input [31:0] ReadData2,outputData;
input ALUSrc;
output [31:0]out_inALU;
reg [31:0]out_inALU;
always #(ReadData2 or outputData or ALUSrc )
begin
case(ALUSrc)
1'b0: out_inALU=ReadData2;
1'b1: out_inALU=outputData;
endcase
end
endmodule
// Mux 2 to 1 5 bit
module MUX_2to1_5bit( inputa , inputb, regDst, WriteReg);
input [4:0] inputa, inputb;
input regDst;
output [4:0]WriteReg;
reg [4:0]WriteReg;
always #(inputa or inputb or regDst )
begin
case(regDst)
1'b0: WriteReg=inputa;
1'b1: WriteReg=inputb;
endcase
end
endmodule
// Mux 2 to 1 for memory register
module MUX_2to1_memreg( result,ReadData,MemtoReg,WriteData);
input [31:0] ReadData,result;
input MemtoReg;
output [31:0] WriteData;
reg [31:0]WriteData;
always #(* )
begin
case(MemtoReg)
1'b0: WriteData= result ;
1'b1: WriteData= ReadData;
endcase
end
endmodule
// Progrma COunter
module PC(input_PC,clock,reset,addr);
input reset,clock;
input [31:0] input_PC;
output reg [31:0] addr;
always #(posedge clock)
begin
if (reset)
addr=0;
else
addr=input_PC+4;
end
endmodule
//Register
module Register_32 ( ReadReg1, ReadReg2, WriteReg,
WriteData, clock, RegWrite,ReadData1, ReadData2);
input [4:0] ReadReg1, ReadReg2, WriteReg;
input [31:0] WriteData;
input clock, RegWrite;
output [31:0] ReadData1, ReadData2;
reg [31:0] ReadData1, ReadData2;
reg [31:0] mem[0:31]; // 32 32-bit registers
reg [5:0] i; // Temporary variable
initial
begin
// Initial registers for testing purpose
for ( i = 0; i <= 31; i = i+1)
mem[i] = i;
// Initial start-up
ReadData1 = 0;
ReadData2 = 0;
end
// Data from register is always fetched with positive edge clock
always #(posedge clock)
begin
#1 ReadData1 = mem[ReadReg1];
#1 ReadData2 = mem[ReadReg2];
if ( RegWrite == 1)
#1 mem[WriteReg] = WriteData;
end
endmodule
// Sign extender
module SignExtender_16to32(immediate,out_sign);
input[15:0] immediate;
output[31:0] out_sign;
reg [31:0] out_sign;
always#(*)
begin
out_sign[15:0] = immediate[15:0];
out_sign[31:16] = {16{immediate[15]}};
end
endmodule

Answer 1

You could increment the program counter as below but it will have wrap around issues. Better to have a signal to latch the input address or at reset do add = input_PC;
module PC(input_PC,clock,reset,addr);
input reset,clock;
input [31:0] input_PC;
output reg [31:0] addr;
always #(posedge clock)
begin
if (reset)
addr= 0;
else
addr=input_PC+4+addr;
end
endmodule
you would want the mem to ignore lower 2 bits in inst module else after reading mem 0 it will read mem[4] .
instruction <= MEM[ addr[31:2] ] ;
You need to connect the instruction to the ALU module , cannot offer any suggestion as i cannot figure what your instruction decoding scheme is.