> According to Jan Axelson's book a 36 ohm resistor is required > in series at each drivers output, to act as source terminations Hmmm, thanks Colin. I guess then that those who don't put them in aren't in spec. I did think maybe there was a termination or impedance reason (like RS485 etc) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist