Wednesday, September 26, 2007

Null Modem for High Availability

Null modem cable pin mapping
This is one very common mapping which will work with software that relies on proper assertion of the CD signal.
Signal Name DB-25 Pin DE-9 Pin
DE-9 Pin DB-25 Pin
FG (Frame Ground) 1 - X - 1 FG
TD (Transmit Data) 2 3 - 2 3 RD
RD (Receive Data) 3 2 - 3 2 TD
RTS (Request To Send) 4 7 - 8 5 CTS
CTS (Clear To Send) 5 8 - 7 4 RTS
SG (Signal Ground) 7 5 - 5 7 SG
DSR (Data Set Ready) 6 6 - 4 20 DTR
CD (Carrier Detect) 8 1 - 4 20 DTR
DTR (Data Terminal Ready) 20 4 - 1 8 CD
DTR (Data Terminal Ready) 20 4 - 6 6 DSR

#Use 1-4 & 4-1 for 9 pin HA null modem.

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