Before I got a Raspberry Pi with home assistant, I was trying to write a simple client for this protocol in C so I could host it on my OpenWRT router. Of course my client bugged and sent some random junk which caused the unit to completely lock up, it displayed 88 on it;s display and didn't respond to the IR remote. After this I had to reset it via the circuit breaker.

If I recall correctly, the data was encrypted using a static AES key, and I think the unit checked if the data decrypted correctly, but don't quote me on that.