Do you mean bytes 0xc0 and 0x80, or the literal strings "xC0" and "x80"?

On second thoughts, I'm not sure if 561 supports serial control for integration purposes; I thought the port on it was for configuration via Meridian.exe only; if that is the case then the protocol is binary (and with a checksum byte IIRC) and not easily spoken by human.

What do you see if you run the port at 9600? (It can't be the same, but how it is different might be telling.)

B.