Hello again,
I was just thinking ... with a master/slave setup, if the code could be written so when an input pin is taken high on either the master or the slave, a corresponding output pin is made high on both the master and slave as long as the input pin is high. Two or more input pins could be made high at any one time from a single button for encoding purposes. I can use latches external to the Arduino to latch data where necessary, that's not a problem at all. There wouldn't be any conflicting activity between the master and slave since only one button on either the master or the slave would be pressed at any one time.
I'd still like to have PWM if possible, but it's not a deal breaker.
Would that make it simpler?
Thanks again.