(b) To get the Signed_Overflow bit (in the following module aluOV) for a 4-bit adder, we can XOR the carry bit C3 (to the MSB slice) with the carry bit C4 (from the MSB slice), see figure Q4-2. Compose HDL code to get C3, C4 and then output Signed_Overflow signal, with necessary comments.
时间: 2024-03-17 12:40:10 浏览: 23
Sure, here is the HDL code for the aluOV module:
```verilog
module aluOV(A, B, Cin, Signed_Overflow, C3, C4);
input [3:0] A, B;
input Cin;
output Signed_Overflow;
output C3, C4;
wire [3:0] Sum;
wire C0, C1, C2, C3_int, C4_int;
// Full adder for LSB slice
full_adder FA0(Sum[0], A[0], B[0], Cin, C0);
// Full adder for second bit slice
full_adder FA1(Sum[1], A[1], B[1], C0, C1);
// Full adder for third bit slice
full_adder FA2(Sum[2], A[2], B[2], C1, C2);
// Full adder for MSB slice
full_adder FA3(Sum[3], A[3], B[3], C2, C3_int);
// Calculate C3 and C4
assign C3 = C3_int ^ C4_int;
assign C4 = C3_int;
// Calculate signed overflow
assign Signed_Overflow = (A[3] == B[3]) && (A[3] != Sum[3]);
endmodule
// Full adder module
module full_adder(Sum, A, B, Cin, Cout);
input A, B, Cin;
output Sum, Cout;
assign Sum = A ^ B ^ Cin;
assign Cout = (A & B) | (Cin & (A ^ B));
endmodule
```
Here, we use four full adders to perform the 4-bit addition, and then use XOR gates to compute the C3 and C4 carry bits. Finally, we use the formula for signed overflow to calculate the output signal.
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