Null-Modem Cable - Pin Out

Document Version: 001b.15-September-2006 Howie Dines

Cables these days are so cheap, it's probabily not worth the time and effort making-up a null-modem cable. ( Also known as a "Laplink Cable" )

However, there is always that one time when you find yourself caught short without one. The following details will help you on the way to make it.

9 Pin D-Sub Connectors RS232 DE-9
(Also, incorrectly known as DB-9 !)

When viewed from the front of the connector. i.e. not the pins solder side. The pin numbering layout used can be seen in the table below.

Signal   Pin(s) Pin(s)          Transmit Data TD 3 2 RD  Receive Data RD 2 3 TD  Request To Send RTS 7 8 CTS  Clear To Send CTS 8 7 RTS  Signal Ground SG 5 5 SG  Data Set Ready  Carrier Detect DSR CD 6 + 1 4 DTR  Data Terminal Ready DTR 4 1 + 6 CD DS