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ALU flag operation added

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Imants Pulkstenis
2020-02-16 15:26:56 +02:00
parent c715347ee5
commit 4b4e427c4a
2 changed files with 82 additions and 26 deletions
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ps2/ps02q/alu.v
+81 -25
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@@ -26,45 +26,101 @@ module alu #( parameter
data_width = 32 data_width = 32
)( )(
input clk, input clk,
input signed [data_width - 1:0] A, input [data_width - 1:0] A,
input signed [data_width - 1:0] B, input [data_width - 1:0] B,
input [3:0] op, input [3:0] op,
output signed [data_width - 1:0] R, output [data_width - 1:0] R,
output flag); output flag);
//define inside of the module //define inside of the module
//define inside use signals and components [part 4 of the VHDL file] //define inside use signals and components [part 4 of the VHDL file]
reg signed [data_width:0] reg_R = 'h0; // width is 33 to capture overflow or underflow reg [data_width :0] reg_R = 'h0; // width is 33 to capture overflow or underflow
reg reg_flag = 'b0;
reg [data_width - 2 : 0 ] reg_max_pos = 'b1; // maximum
//define the operation of the module! [part 5 of the VHDL file] //define the operation of the module! [part 5 of the VHDL file]
always@(posedge clk) begin always@(posedge clk) begin
case (op) case (op)
4'h0: reg_R <= A - B; 4'h0: begin
4'h1: reg_R <= A + B; reg_R <= A - B;
4'h2: reg_R <= ~(A & B); if ( B > A ) begin
4'h3: reg_R <= A & B; reg_flag = 'b1;
4'h4: reg_R <= A | B; end
4'h5: reg_R <= ~(A | B); else reg_flag = 'b0;
4'h6: reg_R <= A ^ B; end
4'h7: reg_R <= ~A; 4'h1: begin
4'h8: reg_R <= ~B; reg_R <= A + B;
4'h9: reg_R <= B + 1; if ((A + B) > reg_max_pos ) begin
4'ha: reg_R <= A + 1; reg_flag = 'b1;
4'hb: reg_R <= A - 1; end
4'hc: reg_R <= B - 1; else reg_flag = 'b0;
4'hd: reg_R <= A << 1; // << Shift Left, Logical (fill with zero) end
// <<< Shift Left, Arithmetic (keep sign) 4'h2: begin
4'he: reg_R <= A >> 1; // >> Shift Right, Logical (fill with zero) reg_R <= ~(A & B);
// >>> Shift Right, Arithmetic (keep sign) reg_flag = 'b0;
4'hf: reg_R <= 'b0; end
default: reg_R <= 'b0; 4'h3: begin
reg_R <= A & B;
reg_flag = 'b0;
end
4'h4: begin
reg_R <= A | B;
reg_flag = 'b0;
end
4'h5: begin
reg_R <= ~(A | B);
reg_flag = 'b0;
end
4'h6: begin
reg_R <= A ^ B;
reg_flag = 'b0;
end
4'h7: begin
reg_R <= ~A;
reg_flag = 'b0;
end
4'h8: begin
reg_R <= ~B;
reg_flag = 'b0;
end
4'h9: begin
reg_R <= B + 1;
if ( B == reg_max_pos ) reg_flag = 'b1;
end
4'ha: begin
reg_R <= A + 1;
if ( reg_max_pos ) reg_flag = 'b1;
end
4'hb: begin
reg_R <= A - 1;
if ( A == {1'b1, ~reg_max_pos } ) reg_flag = 'b1;
end
4'hc: begin
reg_R <= B - 1;
if ( B == {1'b1, ~reg_max_pos } ) reg_flag = 'b1;
end
4'hd: begin
reg_R <= A << 1; // << Shift Left, Logical (fill with zero)
reg_flag = 'b0; // <<< Shift Left, Arithmetic (keep sign)
end
4'he: begin
reg_R <= A >> 1; // >> Shift Right, Logical (fill with zero)
reg_flag = 'b0; // >>> Shift Right, Arithmetic (keep sign)
end
4'hf: begin
reg_R <= 'b0;
reg_flag = 'b0;
end
default: begin
reg_R <= 'b0;
reg_flag = 'b0;
end
endcase endcase
end end
assign R = reg_R[data_width - 1:0]; assign R = reg_R[data_width - 1:0];
assign flag = (reg_R[data_width]==1'b1) ? 1'b1 : 1'b0; //optional assign flag = reg_flag; //optional
endmodule endmodule