Livt.Signal

src/stream/Q15SampleFifo.lvt

namespace Livt.Signal.Stream

using Livt.Collections

/**
 * Buffers complete Q1.15 stream tokens in a packed single-clock FIFO.
 * Capacity is measured in samples. The oldest token is visible without a pop;
 * a transfer removes it only when valid and ready are both true at an active edge.
 */
component Q15SampleFifo<CAPACITY: int = 16>
{
	static assert CAPACITY > 0, "Q15 sample FIFO capacity must be positive"

	// Borrowed input and output stream endpoints.
	inputStream: IQ15SampleStream
	outputStream: IQ15SampleStream

	// Packed FIFO request and response signals: sample[15:0], first[16], last[17].
	fifo: Fifo<logic[18], CAPACITY>
	push: bool
	pushData: logic[18]
	pop: bool
	pushAccepted: bool
	popAccepted: bool
	popData: logic[18]
	count: int
	space: int
	clear: bool

	/**
	 * Binds a consumer-side input and producer-side output in one clock/reset context.
	 */
	new(inputStream: IQ15SampleStream, outputStream: flip IQ15SampleStream)
	{
		this.inputStream = inputStream
		this.outputStream = outputStream
		fifo = new Fifo<logic[18], CAPACITY>(clear, push, pushData, pop,
			pushAccepted, popAccepted, popData, count, space)
	}

	/**
	 * Packs incoming tokens and maps FIFO acceptance to valid/ready flow control.
	 */
	process Drive[]()
	{
		clear = false
		push = inputStream.valid
		pop = outputStream.ready
		pushData = inputStream.sample as logic[18]

		if (inputStream.first) {
			pushData[16] = 0b1
		} else {
			pushData[16] = 0b0
		}

		if (inputStream.last) {
			pushData[17] = 0b1
		} else {
			pushData[17] = 0b0
		}

		inputStream.ready = pushAccepted
		outputStream.valid = this.context.rst == 0b0 && count > 0
		outputStream.sample = popData[0: 16]
		outputStream.first = popData[16] == 0b1
		outputStream.last = popData[17] == 0b1
	}
}