Consider two 4-bit binary numbers A and B. Bits of A are a3, a2, a1, and a0, and bits of B are b3, b2, b1, and b0. A is greater than B if a3 is 1 and b3 is 0, but if a3 and b3 are the same, then if a2 is 1 and b2 is 0, we can determine that A is greater than B. This evaluation continues until a0 and b0 are considered. If a0 and b0 are equal then A and B are equal. Using discrete gates and Verilog gate primitives build a 4-bit comparator that generates a 1 on its GT output when its 4-bit input A is greater than its B input, and a 1 on its EQ output when A and B are equal. Use the generate statement and other Verilog iterative logic support structures.
时间: 2023-12-23 15:06:20 浏览: 19
Here's the Verilog code for a 4-bit comparator that generates a 1 on its GT output when its 4-bit input A is greater than its B input, and a 1 on its EQ output when A and B are equal:
```
module comparator (
input [3:0] A,
input [3:0] B,
output reg GT,
output reg EQ
);
reg [3:0] a_xor_b;
reg [2:0] a_gte_b;
assign a_xor_b = A ^ B;
generate
for (i = 2; i >= 0; i--) begin
assign a_gte_b[i] = (A[i] == B[i]) ? a_gte_b[i+1] : A[i];
end
endgenerate
always @(*) begin
if (A[3] == 1 && B[3] == 0) begin
GT = 1;
EQ = 0;
end else if (A[3] == B[3] && a_gte_b[0] == 1) begin
GT = 1;
EQ = 0;
end else if (a_xor_b == 0) begin
GT = 0;
EQ = 1;
end else begin
GT = 0;
EQ = 0;
end
end
endmodule
```
The `a_xor_b` register holds the result of XORing the two 4-bit inputs A and B. The `a_gte_b` register is used to determine if A is greater than or equal to B. It is generated using a generate statement that iteratively compares each bit of A and B starting from the most significant bit. If the bits are equal, it copies the value from the previous iteration, otherwise it copies the value of the corresponding bit in A.
The `always` block evaluates the conditions for A being greater than, equal to, or less than B. If the most significant bit of A is 1 and the most significant bit of B is 0, then A is greater than B. If the most significant bits are the same, then it checks the `a_gte_b` register starting from the most significant bit to determine if A is greater than or equal to B. If A and B are equal, then the `a_xor_b` register will be 0. Otherwise, A is less than B.
The `GT` and `EQ` outputs are set accordingly based on the evaluation in the `always` block.