Sure, here's an example of a 4-bit magnitude comparator implemented using only NOR gates in SystemVerilog:
module magnitude_comparator_4bit_nor(
input logic [3:0] a,
input logic [3:0] b,
output logic eq,
output logic gt,
output logic lt
);
logic [3:0] na, nb, diff;
assign na =
a; assign nb =
b;
assign diff = na + b;
assign eq =
(diff[3] | diff[2] | diff[1] | diff[0]); assign gt =
(na[3] & nb[3] & diff[3]) &
(na[3] & nb[2] & diff[2]) &
(na[3] & nb[1] & diff[1]) &
(na[3] & nb[0] & diff[0]); assign lt =
(a[3] & b[3] & diff[3]) &
(a[3] & b[2] & diff[2]) &
(a[3] & b[1] & diff[1]) &
(a[3] & b[0] & diff[0]); endmodule
In this code, we define a module called `magnitude_comparator_4bit_nor` with two input ports `a` and `b`, and three output ports `eq`, `gt`, and `lt`. The `a` and `b` inputs are 4-bit binary values representing the two numbers to be compared, and the `eq`, `gt`, and `lt` outputs are single-bit binary values representing the comparison results.
The `na`, `nb`, and `diff` signals are 4-bit binary values representing the bitwise NOT of `a`, the bitwise NOT of `b`, and the difference between `na` and `b`, respectively.
The `assign` statements use NOR gates to implement the magnitude comparison logic. The `eq` output is set to 1 if the two inputs are equal, which is the case when the difference between `na` and `b` is 0. The `gt` output is set to 1 if `a` is greater than `b`, which is the case when the most significant bit of `na` is 1 and the most significant bit of `nb` is 0, and the difference between `na` and `b` is positive. The `lt` output is set to 1 if `a` is less than `b`, which is the case when the most significant bit of `a` is 0 and the most significant bit of `b` is 1, and the difference between `na` and `b` is negative.
You can instantiate this module in your top-level design hierarchy and connect it to other modules or input/output signals as needed. Note that you can modify the code to implement a magnitude comparator with a different number of bits by changing the bit width of the input and output signals, and modifying the magnitude comparison logic accordingly.