The cable is just wires hooked to pins. It's the device that matters. I think of the RXD pin on the device going to the receive pin on it's UART. The TXD on one device goes to the RXD on the other device. If both devices use the same pin for RXD then you need to cross the RXD & TXD wires before they get to the other device. This is called a "Null Modem" cable.. This is not a complete answer but I am tired, hungry and Pookie says "It's time for noon nap." Bill ----- Original Message ----- From: "Vic Fraenckel" To: "PICMIT" Sent: Tuesday, July 19, 2005 10:33 AM Subject: [EE] Clairfy RS232 signal directions Given an RS232 cable with just 3 wires thus: Pin 2 - RXD Pin3 - TXD Pin5 - GND connected to a DB9 on a computer and going to some sort of device. 1. Is this the proper way to name the wires? 2. Does RXD imply a signal going TO a computer FROM the device? 3. Does TXD imply a signal coming FROM a computer TO the device? This always confuses me but I seem to be able to muddle through. Any enlightenment will be appreciated. Regards, Vic ________________________________________________________ Victor Fraenckel - The Windman victorf ATSIGN windreader DOTcom KC2GUI -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist