Method: HDLRuby::High::Std#delay

Defined in:
lib/HDLRuby/std/delays.rb

#delay ⇒ Object

Module describing a simple delay using handshake for working. @param num the number of clock cycles to delay.



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# File 'lib/HDLRuby/std/delays.rb', line 11

system :delay do |num|
    # Checks and process the number of clock to wait.
    num = num.to_i
    raise "The delay generic argument must be positive: #{num}" if (num < 0)

    input  :clk     # The clock to make the delay on.
    input  :req     # The handshake request.
    output :ack     # The handshake acknoledgment.

    # The process of the delay.
    if (num == 0) then
        # No delay case.
        ack <= req
    else
        # The is a delay.
        inner run: 0               # Tell if the deayl is running.
        [num.width+1].inner :count # The counter for computing the delay.
        par(clk.posedge) do
            # Is there a request to treat?
            hif(req & ~run) do
                # Yes, intialize the delay.
                run <= 1
                count <= 0
                ack <= 0
            end
            # No, maybe there is a request in processing.
            helsif(run) do
                # Yes, increase the counter.
                count <= count + 1
                # Check if the delay is reached.
                hif(count == num-1) do
                    # Yes, tells it and stop the count.
                    ack <= 1
                    run <= 0
                end
            end
        end
    end
end