I need to send data (one or several bytes) from the first MCU to another when it has some. The second does the same sending data to the first MCU. Can you recommend a simple and reliable protocol?
I can use port 2 in low - level interrupt mode. This means that when one of the 8 pins is asserted low an interrupt is generated. This would allow an MCU to select its neighbour interrupting it. The interrupted MCU would accept data and ack. Deasserting the pin would signal "transfer is done" conition.
One of the ports can be used as a 8bit bi-dir data bus. One of the MCUs can be a master.
I only aware of synch/asynch schemes used in HW machines. Not sure how data transfer typically is done between MCUs. Thanks.