If there's a single rising edge on the bus that you can use as quantum trigger, then, the reads turn into as series of moves into a FIFO, and the response can b

If there's a single rising edge on the bus that you can use as quantum trigger, then, the reads turn into as series of moves into a FIFO, and the response can be quite fast. The quantum-trigger-on-GPIO was provided to solve exactly the problem you described.