Designing an Arbiter in Verilog and SystemVerilog

An arbiter is a digital circuit that selects one of several requesters based on some predefined priority scheme. An arbiter can be used in various applications, including memory controllers, shared buses, and communication systems.

In this post, we will discuss how to design an arbiter in Verilog and SystemVerilog. We will use fixed priority and always_comb statement to implement an arbiter that selects one of the requesters based on priority.

Designing a Fixed Priority Arbiter in Verilog and SystemVerilog

A fixed priority arbiter selects one of the requesters based on a predefined priority scheme. In a fixed priority arbiter, the highest priority request is granted access first. If multiple requests have the same priority, the arbiter selects one of the requests in a round-robin fashion.

The following code shows an example implementation of a fixed priority arbiter in Verilog and SystemVerilog:

module Arbiter #(
  parameter NumRequests = 4
) (
  input  logic [NumRequests-1:0] request,
  output logic [NumRequests-1:0] grant
);

  always_comb begin
    grant = '0;

    for (int i = 0; i < NumRequests; i++) begin
      if (request[i]) begin
        grant[i] = 1;
        break;
      end
    end
  end

endmodule

In this implementation, the input signal request is a NumRequests-bit vector that indicates which requesters are requesting access. The output signal grant is also a NumRequests-bit vector that indicates which requester is granted access.

The always_comb block uses a for loop to iterate through all of the requests and select the highest priority requester. If multiple requests have the same priority, the arbiter selects one of the requests in a round-robin fashion.

Conclusion

In this post, we have discussed how to design an arbiter in Verilog and SystemVerilog. We have used a fixed priority scheme and always_comb statement to implement an arbiter that selects one of the requesters based on priority. The specific design of an arbiter depends on the specific requirements of the application, including the number of requesters, the priority scheme, and the arbitration policy.