Signals in Verilog
Here’s an idiomatic Verilog example demonstrating a concept similar to signal handling:
module signal_handler (
input wire clk,
input wire reset,
input wire signal_interrupt,
input wire signal_terminate,
output reg [7:0] status
);
// Define states
localparam IDLE = 2'b00;
localparam RUNNING = 2'b01;
localparam INTERRUPTED = 2'b10;
localparam TERMINATED = 2'b11;
reg [1:0] state;
reg [1:0] next_state;
// State transition logic
always @(posedge clk or posedge reset) begin
if (reset)
state <= IDLE;
else
state <= next_state;
end
// Next state and output logic
always @(*) begin
next_state = state;
status = 8'h00;
case (state)
IDLE: begin
status = 8'h01;
if (signal_interrupt || signal_terminate)
next_state = RUNNING;
end
RUNNING: begin
status = 8'h02;
if (signal_interrupt)
next_state = INTERRUPTED;
else if (signal_terminate)
next_state = TERMINATED;
end
INTERRUPTED: begin
status = 8'h03;
next_state = IDLE;
end
TERMINATED: begin
status = 8'h04;
// Stay in TERMINATED state
end
default: next_state = IDLE;
endcase
end
endmodule
This Verilog module demonstrates a concept similar to signal handling in a hardware context. Let’s break down the code and its functionality:
The module
signal_handler
has inputs for clock (clk
), reset (reset
), and two signals (signal_interrupt
andsignal_terminate
). It outputs an 8-bitstatus
register.We define four states using localparams:
IDLE
,RUNNING
,INTERRUPTED
, andTERMINATED
.The module uses a two-process state machine model:
- The first always block handles state transitions on the rising edge of the clock or reset.
- The second always block is combinational and determines the next state and output based on the current state and inputs.
The state machine behaves as follows:
- In the
IDLE
state, it waits for either signal to transition to theRUNNING
state. - In the
RUNNING
state, it checks forsignal_interrupt
orsignal_terminate
. - If interrupted, it goes to the
INTERRUPTED
state and then back toIDLE
. - If terminated, it goes to the
TERMINATED
state and stays there.
- In the
The
status
output changes based on the current state, providing information about the module’s status.
To simulate this Verilog module, you would typically create a testbench that instantiates the module and provides clock and input signals. You can use a Verilog simulator like ModelSim, Icarus Verilog, or Verilator to run the simulation.
This example demonstrates how to handle different signals in a hardware design, which is conceptually similar to signal handling in software, but implemented using hardware description language constructs like state machines and synchronous logic.