Bruce Bowling wrote: >I wish to take 8 digital channels and multiplex them >down one fiber optic cable, and demux them back into >8 channels. The fastest changing signal is around >0.1 milliseconds. I think it is time for a sanity check here. First of all, does the last sentence above imply that you expect to update each channel every 100 microseconds? Let's see .. 8 bits every 100 microcseconds is 12.5 microseconds/bit or 80kb/s. And this is just for one channel and assumes only 8 bit resolution. Add in some identification bits (three minimum) and the other channels and you are near 1 microsecond/bit. With a 20mHz PIC this is only 5 instructions. It would seem that at a minimum a UART will be needed. The UART will have to run at 1mb/s. Will your communications channel handle this? -- Bob Fehrenbach Wauwatosa, WI bfehrenb@execpc.com