Greg, that operator panel was originally for a 15 (I think) I have the same one on my cnc bridgeport...I wrote a panel decoding ladder (leave 'operator panel' otion off when compiling the ladder) thats already functional for prettymuch anything on there(I didnt program the teach functions, but you can see in the ladder how to easily add rungs for each key/led).

the board on the back of these panels is for I/O multiplexing, theres 3 bits as 'byte adders'- 000= byte 292, 001=byte 293, so on thru 111=byte 299...theres a strobe bit, and raw bit 0~7... the output is a kinda unsynchronized strobe pattern (why some zeroes flash all the leds at boot up once in a while...)

anyhow, next time I get the chance I can send you the ladder (text/printable copy- its for a 0-a, not a 0-c) and might be something there you can use...Ive got a good timing drawing of the panel signals, drawing of the more common panel with addressing right on the keys (always hated how fanuc 'showed' the addressing via tables...)