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
    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
    end else if (op == JAL)begin
        CtrlRegDst = 2'd2; //const reg 31, for writing to the link register
    end else begin CtrlRegDst = 1'bx; 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
        $display("Ctrl PC Branch");
    end else if( (op == J | op == JAL))begin
        CtrlPC = 2'd2; // Jumps within 256MB Region using 26-bit immediate in J type instruction
        $display("Ctrl PC Jump Immediate");
    end else if((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
    end else if ((op == ADDIU | op == ANDI | op == ORI | op == SLTI | op == SLTIU | op == XORI | (op == SPECIAL & (funct == (ADDU | AND | DIV | DIVU | MTHI | MTLO | MULT | MULTU | OR |  SLL | SLLV | SLT | SLTU | SRA | SRAV | SRL | SRLV | SUBU | XOR)))))begin
        CtrlMemRead = 0;//Memory is read disabled
        CtrlMemtoReg = 2'd0;//write data port of memory is fed from ALURes
    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
    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
    end else if (op == LUI)begin
        CtrlALUOp = 5'd7;//SLL from ALUOps
    end else if ((op == SPECIAL & (funct == MTHI | 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
    end else if (op == SPECIAL & (funct == SLLV))begin
        CtrlALUOp = 5'd8;//SLLV from ALUOps
    end else if (op == SPECIAL & (funct == SRA))begin
        CtrlALUOp = 5'd11;//SRA from ALUOps
    end else if (op == SPECIAL & (funct == SRAV))begin
        CtrlALUOp = 5'd12;//SRAV from ALUOps
    end else if (op == SPECIAL & (funct == SRL))begin
        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
    end else if (op == SLTIU | (op == SPECIAL & (funct == SLTU)))begin
        CtrlALUOp = 5'd21;//SLTU from ALUOps
    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
    end else begin
        CtrlALUOp = 5'bxxxxx;
    end

    //Ctrlshamt logic
    if(op == SPECIAL & (funct == (SRA | SRL | 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 == REGIMM & ((rt == BGEZ | rt == BGEZAL | rt == BLTZ | rt == BLTZAL))) | (op == SPECIAL & ((funct == ADDU | funct == AND | funct == DIV | funct == DIVU | funct == MULT | funct == MULTU | funct == OR | funct == SLLV | funct == SLT | funct == SLTU | funct == SRAV | funct == SRLV | funct == SUBU | funct == XOR)))))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 == SLTIU | op == XORI | (op == SPECIAL & ((funct == ADDU | funct == AND | funct == DIV | funct == DIVU | funct == MULT | funct == MULTU | 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
        CtrlRegWrite = 1;//The Registers are Write Enabled
    end else begin CtrlRegWrite = 0; end // The Registers are Write Disabled

end
endmodule