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decodeFamilies.v
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/* Decode Logic for Identifying Decode Families
* Started By: Vickie
*/
/* Decode Families Key:
* Index Description
* f[0] Data Processing Immediate
* f[1] Data Processing Immediate Shift
* f[2] Data Processing Register Shift
* f[3] Multiply
* f[4] Multiply Long
* f[5] Move from Status Register
* f[6] Move Immediate to Status Register
* f[7] Move Register to Status Register
* f[8] Load/Store Immediate Offset
* f[9] Load/Store Register Offset
* f[10] Load/Store Halfword/Signed Byte Combined Offset
* f[11] Load/Store Halfword/Signed Byte Shifted Offset
* f[12] Swap/Swap Byte
* f[13] Load/Store Multiple
* f[14] Branch and Branch with Link
* f[15] Undefined Instruction
*/
module decodeFamily (
input [31:0] ir,
output reg [15:0] f_signals,
output reg [3:0] f_num
);
wire [15:0] mask = 16'h0001;
always @ (ir)
case (ir[27:25])
3'b000 : begin
if ((ir[24:22] == 3'b000) && (ir[7:4] == 4'b1001)) begin //f3
f_signals = (mask << 3);
f_num = 3;
end
else if ((ir[24:23] == 2'b01) && (ir[7:4] == 4'b1001)) begin //f4
f_signals = (mask << 4);
f_num = 4;
end
else if ((ir[24:23] == 2'b10) && (ir[21:20] == 2'b00)) begin
if (ir[7:4] == 4'b1001) begin //f12
f_signals = (mask << 12);
f_num = 12;
end
else begin //f5
f_signals = (mask << 5);
f_num = 5;
end
end
else if (((ir[24:23] == 2'b10) && (ir[21:20] == 2'b10)) && (ir[4] == 1'b0)) begin //f7
f_signals = (mask << 7);
f_num = 7;
end
else if (ir[4] == 1'b0) begin //f1
f_signals = (mask << 1);
f_num = 1;
end
else begin
if (ir[7] == 1'b0) begin //f2
f_signals = (mask << 2);
f_num = 2;
end
else begin
if (ir[22] == 1'b0) begin //f11
f_signals = (mask << 11);
f_num = 11;
end
else begin //f10
f_signals = (mask << 10);
f_num = 10;
end
end
end
end
3'b001 : begin
if ((ir[24:23] == 2'b10) && (ir[21:20] == 2'b10)) begin //f6
f_signals = (mask << 6);
f_num = 6;
end
else begin //f0
f_signals = (mask << 0);
f_num = 0;
end
end
3'b010 : begin //f8
f_signals = (mask << 8);
f_num = 8;
end
3'b011 : begin
if (ir[4] == 1'b0) begin //f9
f_signals = (mask << 9);
f_num = 9;
end
else begin //f15
f_signals = (mask << 15);
f_num = 15;
end
end
3'b100 : begin //f13
f_signals = (mask << 13);
f_num = 13;
end
3'b101 : begin //f14
f_signals = (mask << 14);
f_num = 14;
end
3'b110 : begin //not implementing these coprocessor instructions
f_signals = 16'h0000;
f_num = 0;
end
3'b111 : begin //not implementing these coprocessor instructions
f_signals = 16'h0000;
f_num = 0;
end
endcase
endmodule