This is in a mode that I am calling RC-10 mode. In this mode the radio will allow you to use any and all of the buttons on the radio itself. It only clocks out data when you operate the controls on the radio or on the remote unit, and then the remote unit acts as the bus master. The radio will only send data out when the clock is running and it is receiving 0xFF on serial in. 1 byte out for each byte in. I'm still not sure how the radio indicates that it has data to send out. I think it may twiddle the serial out line a bit. I am currently unable to emulate even this mode so far. I may have to write some sort of bit bang code in order to get the Bus Pirate to handle UART in/out and also the clock line.
The other mode I am calling RC-20 mode and it's a little more mysterious, to me. If I hold RD high, and keep it high, then send something, anything, down serial in then the radio will start continuously sending display frames out the serial out line. It also clocks the clock line itself. I can't seem to make it see any data that I send after that point. Additionally, in contrast to the other mode of operation, once in this mode the radio completely ignores all operation of the controls on the radio itself. There must be some sort of protocol that I'm missing. Maybe something like pull the serial in line high for 50ms, then clock data in or something. Come to think of it, in this mode there is a one shot chance of changing the frequency. Sometimes it works once and then not again until I reset the radio. I wonder if I sent some 0xFF bytes down the line after that if it would work again. But then again, in the other made that only seems to happen so the radio will send out display packets. It does that anyways in this mode. It bears further experimentation.