verilog 3to 1arbitration

Here is an example of a Verilog code for a 3-to-1 arbitration circuit:

module arbiter(input [2:0] req, // Three request signals
input clk, // Clock
output reg grant); // Grant signal

reg [1:0] state; // State variable

always @(posedge clk) begin
case (state)
2'b00: begin // State 0 - Wait for requests
if (req[0] == 1) // If request 0 is asserted
state <= 2'b01; // Move to state 1
else if (req[1] == 1) // If request 1 is asserted
state <= 2'b10; // Move to state 2
end
2'b01: begin // State 1 - Grant request 0
grant <= 1; // Assert grant signal
if (req[1] == 1) // If request 1 is asserted
state <= 2'b10; // Move to state 2
else
state <= 2'b00; // Move to state 0
end
2'b10: begin // State 2 - Grant request 1
grant <= 1; // Assert grant signal
if (req[0] == 1) // If request 0 is asserted
state <= 2'b01; // Move to state 1
else
state <= 2'b00; // Move to state 0
end
endcase
end

endmodule

In this code, the three request signals (req) are input to the module along with the clock signal (clk), and the grant signal is output. The module has a state variable (state) which determines which request signal to grant.

In the initial state (state=2'b00), the module waits for any of the three request signals to be asserted. If request 0 (req[0]) is asserted, the module moves to state 1 (2'b01) and grants request 0 by asserting the grant signal. If request 1 (req[1]) is asserted, the module moves to state 2 (2'b10) and grants request 1.

Once a request is granted, the module checks the other two request signals to see if they are still asserted. If another request is asserted, the module moves to the corresponding state and grants that request. If no other requests are asserted, the module returns to the initial state and waits for a new request to be asserted.