ELEC50010-IAC-CW/rtl/mips_cpu_control.v

module mips_cpu_control(
    input logic[31:0] Instr,
    input logic ALUCond,
    
    output logic[1:0] CtrlRegDst,
    output logic[1:0] CtrlPC,
    output logic CtrlMemRead,
    output logic[1:0] CtrlMemtoReg,
    output logic[4:0] CtrlALUOp,
    output logic[4:0] Ctrlshamt,
    output logic CtrlMemWrite,
    output logic CtrlALUSrc,
    output logic CtrlRegWrite
);

typedef enum logic[5:0]{
    SPECIAL = 6'd0,
    REGIMM  = 6'd1,
    J       = 6'd2,
    JAL     = 6'd3,
    BEQ     = 6'd4,
    BNE     = 6'd5,
    BLEZ    = 6'd6,
    BGTZ    = 6'd7,
    ADDI    = 6'd8,
    ADDIU   = 6'd9,
    SLTI    = 6'd10,
    SLTIU   = 6'd11,
    ANDI    = 6'd12,
    ORI     = 6'd13,
    XORI    = 6'd14,
    LUI     = 6'd15,
    LB      = 6'd32,
    LH      = 6'd33,
    LWL     = 6'd34,
    LW      = 6'd35,
    LBU     = 6'd36,
    LHU     = 6'd37,
    LWR     = 6'd38,
    SB      = 6'd40,
    SH      = 6'd41,
    SW      = 6'd43
} op_enum;
op_enum op;
assign op = Instr[31:26];

typedef enum logic[5:0]{
    SLL     = 6'd0,
    SRL     = 6'd2,
    SRA     = 6'd3,
    SLLV    = 6'd4,
    SRLV    = 6'd6,
    SRAV    = 6'd7,
    JR      = 6'd8,
    JALR    = 6'd9,
    MTHI    = 6'd17,
    MTLO    = 6'd19,
    MULT    = 6'd24,
    MULTU   = 6'd25,
    DIV     = 6'd26,
    DIVU    = 6'd27,
    ADDU    = 6'd33,
    SUBU    = 6'd35,
    AND     = 6'd36,
    OR      = 6'd37,
    XOR     = 6'd38,
    SLT     = 6'd42,
    SLTU    = 6'd43
} funct_enum;
funct_enum funct;
assign funct = Instr[5:0];

typedef enum logic[4:0]{
    BLTZ    = 5'd0,
    BGEZ    = 5'd1,
    BLTZAL  = 5'd16,
    BGEZAL  = 5'd17
} rt_enum;
rt_enum rt;
assign rt = Instr[20:16];



always @(*) begin
    //CtrlRegDst logic
    if((op==ADDIU) || (op==ANDI) || (op==LB) || (op==LBU) || (op==LH) || (op==LHU) || (op==LUI) || (op==LW) || (op==LWL) || (op==LWR) || (op==ORI) || (op==SLTI) || (op==SLTIU) || (op==XORI))begin
        CtrlRegDst = 2'd0; //Write address comes from rt
        $display("CTRLREGDST: Rt");
    end else if ((op==SPECIAL)&&((funct==ADDU) || (funct==AND) || (funct==JALR) || (funct==OR) || (funct==SLL) || (funct==SLLV) || (funct==SLT) || (funct==SLTU) || (funct==SRA) || (funct==SRAV) || (funct==SRL) || (funct==SRLV) || (funct==SUBU) || (funct==XOR)))begin
        CtrlRegDst = 2'd1; //Write address comes from rd
        $display("CTRLREGDST: Rd");
    end else if (op == JAL)begin
        CtrlRegDst = 2'd2; //const reg 31, for writing to the link register
        $display("CTRLREGDST: Link");
    end else begin CtrlRegDst = 1'bx; $display("xxxxxxxxxxxxxx");end//Not all instructions are encompassed so, added incase for debug purposes

    //CtrlPC logic
    if(ALUCond && ((op==BEQ) || (op==BGTZ) || (op==BLEZ) || (op==BNE) || ((op==REGIMM)&&((rt==BGEZ) || (rt==BGEZAL) || (rt==BLTZ) || (rt==BLTZAL)))))begin
        CtrlPC = 2'd1; // Branches - Jumps relative to PC
    end else if((op==J) || (op==JAL))begin
        CtrlPC = 2'd2; // Jumps within 256MB Region using 26-bit immediate in J type instruction
        $display("Jump PC Ctrl");
    end else if((op==SPECIAL)&&(funct==JR) || (funct==JALR))begin
        CtrlPC = 2'd3; // Jumps using Register.
        //$display("Ctrl PC Jump Register");
    end else begin CtrlPC = 2'd0; /*/$display("Ctrl PC No Jump/Branch");*/end // No jumps or branches, just increment to next word

    //CtrlMemRead and CtrlMemtoReg logic -- Interesting quirk that they have the same logic. Makes sense bc you'd only want to select the read data out when the memory itself is read enabled.
    if((op==LB) || (op==LBU) || (op==LH) || (op==LHU) || (op==LW) || (op==LWL) || (op==LWR))begin
        CtrlMemRead = 1;//Memory is read enabled
        CtrlMemtoReg = 2'd1;//write data port of memory is fed from data memory
        $display("Memory read enabled");
    end else if ((op==ADDIU) || (op==ANDI) || (op==ORI) || (op==SLTI) || (op==SLTIU) || (op==XORI) || ((op==SPECIAL)&&((funct==ADDU) || (funct==AND) || (funct==DIV) || (funct==DIVU) ||  (funct==MTHI) ||  (funct==MTLO) ||  (funct==MULT) ||  (funct==MULTU) ||  (funct==OR) ||  (funct==SLL) ||  (funct==SLLV) ||  (funct==SLT) ||  (funct==SLTU) ||  (funct==SRA) ||  (funct==SRAV) ||  (funct==SRL) || (funct==SRLV) ||  (funct==SUBU) ||  (funct==XOR))))begin
        CtrlMemRead = 0;//Memory is read disabled
        CtrlMemtoReg = 2'd0;//write data port of memory is fed from ALURes
        $display("Memory read disabled");
    end else if ((op==JAL) || ((op==SPECIAL)&&(funct == JALR)))begin
        CtrlMemtoReg = 2'd2;//write data port of memory is fed from PC + 8
    end else begin CtrlMemRead = 1'bx;end//Not all instructions are encompassed so, added incase for debug purposes

    //CtrlALUOp Logic
    if((op==ADDIU) || ((op==SPECIAL)&&(funct==ADDU)))begin
        CtrlALUOp = 5'd0; //ADD from ALUOps
        $display("ALU OP = 0 (ADDU/ADDIU)");
    end else if((op==ANDI) || ((op==SPECIAL)&&(funct==AND)))begin
        CtrlALUOp = 5'd4;//AND from ALUOps
    end else if(op==BEQ) begin
        CtrlALUOp = 5'd13;//EQ from ALUOps
    end else if((op==REGIMM)&&((rt==BGEZ) || (rt==BGEZAL)))begin
        CtrlALUOp = 5'd17;//GEQ from ALUOps
    end else if(op==BGTZ)begin
        CtrlALUOp = 5'd16;//GRT from ALUOps
    end else if(op==BLEZ)begin
        CtrlALUOp = 5'd15;//LEQ from ALUOps
    end else if((op==REGIMM)&&((rt==BLTZ) || (rt==BLTZAL)))begin
        CtrlALUOp = 5'd14;//LES from ALUOps
    end else if(op==BNE)begin
        CtrlALUOp = 5'd18;//NEQ from ALUOps
    end else if((op==SPECIAL)&&(funct==DIV))begin
        CtrlALUOp = 5'd3;//DIV from ALUOps
    end else if((op==SPECIAL)&&(funct==DIVU))begin
        CtrlALUOp = 5'd23;//DIVU from ALUOps
    end else if((op==LB) || (op==LBU) || (op==LH) || (op==LHU) || (op==LW) || (op==LWL) || (op==LWR) || (op==SB) || (op==SH) || (op==SW))begin
        CtrlALUOp = 5'd0;//ADD from ALUOps
        $display("LB IN CONTROL");
    end else if(op==LUI)begin
        CtrlALUOp = 5'd7;//SLL from ALUOps
    end else if((op==SPECIAL)&&((funct==MTHI) || (funct==MTLO)))begin
        CtrlALUOp = 5'd19;//PAS from ALUOps
    end else if((op==SPECIAL)&&(funct==MULT))begin
        CtrlALUOp = 5'd2;//MUL from ALUOps
    end else if((op==SPECIAL)&&(funct==MULTU))begin
        CtrlALUOp = 5'd22;//MULU from ALUOps
    end else if((op==ORI) || ((op==SPECIAL)&&(funct==OR)))begin
        CtrlALUOp = 5'd5;//OR from ALUOps
    end else if((op==SPECIAL)&&(funct==SLL))begin
        CtrlALUOp = 5'd7;//SLL from ALUOps
        $display("ALU Op = 7 (SLL)");
    end else if((op==SPECIAL)&&(funct==SLLV))begin
        CtrlALUOp = 5'd8;//SLLV from ALUOps
        $display("ALU Op = 9 (SLLV)");
    end else if((op==SPECIAL)&&(funct==SRA))begin
        CtrlALUOp = 5'd11;//SRA from ALUOps
        $display("ALU Op = 11 (SRA)");
    end else if((op==SPECIAL)&&(funct==SRAV))begin
        CtrlALUOp = 5'd12;//SRAV from ALUOps
    end else if((op==SPECIAL)&&(funct==SRL))begin
        $display("ALU Op = 7 (SRL)");
        CtrlALUOp = 5'd9;//SRL from ALUOps
    end else if((op==SPECIAL)&&(funct==SRLV))begin
        CtrlALUOp = 5'd10;//SRLV from ALUOps
    end else if((op==SLTI) || ((op==SPECIAL)&&(funct==SLT)))begin
        CtrlALUOp = 5'd20;//SLT from ALUOps
        $display("ALU Op = 20 (SLT/SLTI)");
    end else if((op==SLTIU) || ((op==SPECIAL)&&(funct==SLTU)))begin
        CtrlALUOp = 5'd21;//SLTU from ALUOps
        $display("ALU Op = 21 (SLTU/SLTIU)");
    end else if((op==SPECIAL)&&(funct==SUBU))begin
        CtrlALUOp = 5'd1;//SUB from ALUOps
    end else if((op==XORI) || ((op==SPECIAL)&&(funct==XOR)))begin
        CtrlALUOp = 5'd6;//XOR from ALUOps
        $display("ALU Op = 6 (XOR)");
    end else begin
        CtrlALUOp = 5'bxxxxx;
    end

    //Ctrlshamt logic
    if((op==SPECIAL)&&((funct==SRA) || (funct==SRL) || (funct==SLL)))begin
        Ctrlshamt = Instr[10:6];// Shift amount piped in from the instruction
    end else if(op == LUI)begin
        Ctrlshamt = 5'd16;//Used specifically to implement LUI as the instruction itslef does not include shamt
    end else begin Ctrlshamt = 5'bxxxxx;end

    //CtrlMemWrite logic
    if((op==SB) || (op==SH) || (op==SW))begin
        CtrlMemWrite = 1;//Memory is write enabled
    end else begin CtrlMemWrite = 0;end//default is 0 to ensure no accidental overwriting.
    
    //CtrlALUSrc logic
    if((op==ADDIU) || (op==ANDI) || (op==LUI) || (op==ORI) || (op==SLTI) || (op==SLTIU) || (op==XORI) || (op==LB) || (op==LBU) || (op==LH) || (op==LHU) || (op==LW) || (op==LWL) || (op==LWR) || (op==SB) || (op==SH) || (op==SW))begin
        CtrlALUSrc = 1;//ALU Bus B is fed from the 16-bit immediate sign extended to 32-bit value taken from Instr[15-0]
    end else if((op==BEQ) || (op==BGTZ) || (op==BLEZ) || (op==BNE) || ((op==SPECIAL)&&((funct==ADDU) || (funct==AND) || (funct==DIV) || (funct==DIVU) || (funct==MULT) || (funct==MULTU) || (funct==OR) || (funct==SLL) || (funct==SLLV) || (funct==SLT) || (funct==SLTU) || (funct==SRA) || (funct==SRAV) || (funct==SRL) || (funct==SRLV) || (funct==SUBU) || (funct==XOR))) || ((op==REGIMM)&&((rt==BGEZ) || (rt==BGEZAL) || (rt==BLTZ) || (rt==BLTZAL))))begin 
        CtrlALUSrc = 0;///ALU Bus B is fed from rt.
    end else begin CtrlALUSrc = 1'bx;end
       
    //CtrlRegWrite logic
    if((op==ADDIU) || (op==ANDI) || (op==LB) || (op==LBU) || (op==LH) || (op==LHU) || (op==LUI) || (op==LW) || (op==LWL) || (op==LWR) || (op==ORI) || (op==SLTI) || (op==XORI) || ((op==SPECIAL)&&((funct==ADDU) || (funct==AND) || (funct==DIV) || (funct==DIVU)  || (funct==MULT) || (funct==MULTU) || (funct==OR) || (funct==SLL) || (funct==SLLV) || (funct==SLT) || (funct==SLTU) || (funct==SRA) || (funct==SRAV) || (funct==SRL) || (funct==SRLV) || (funct==SUBU) || (funct==XOR)))) begin
        CtrlRegWrite = 1;//The Registers are Write Enabled
    end else begin CtrlRegWrite = 0;end // The Registers are Write Disabled
end
endmodule