Hi Michael,

You need control of the direction of the communications with half-duplex RS485.

That's why I need the CTS signal.

A master-slave system is easiest to set up. A faulty slave can be made to shut up by a watchdog timer process if necessary.

You must be able to implement a kind of CDMA system with it too, if you detect framing errors (Dallas CPUs seem to be able o detect framing problems)

You have also spotted that Multi-processor comms with an 8052 still takes lots of code support. I always thought that the whole point of this 9 bit mode was that it unloaded the CPU until you were addressed, but it isn't that simple.

Our program uses a an interrupt driven serial routine which is a state machine to read in and parse addresses, commands and arguments from the interface. We transmit binary data in a fixed length format to and from the addressed slaves.

Steve