I've been using 2 ports on 8051 for txer & rxer. Port 2 is for data on both sides and P3.0 and 3.1 are the control on each side(Transmit request/accept & receive req/acc).
There is a protocol whereby you must wait until for the RPC to set TXA to say data accepted and sent, and i'm using CPL LED on the txer to see this. It sends one nibble(LED off) but refuses to send the MSnibble(led stays off).
However, the rxer doesnt acknowledge receipt of the LSnibble(again using LED to check). I've rechecked the connections and they seem grand, could it be I need to set P2/P3 to output/input before writing/reading from them? The datasheet gives mention of a control byte being the 1st byte but doesnt explicitly say if I need to send it or if it does it automatically. Any ideas appreciated!