[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: DB-9 Null Modem Cable



 
> On a modem cable, the RS-232 RX & TX lines are wired straight through, that is
> pin 2 on one end of the cable is wired to pin 2 on the other end, and pin 3 is
> also wired to pin 3.
> 
> On a null-modem cable, the TX and RX pins are swapped on one end of the cable so
> that RX is connected to TX, and vice versa; pin 2 on one end is connected to pin
> 3 on the other end, and pin 3 is connected to pin 2.
> 
 Null modem cables usually have pins 6,8 (6,1) tied to pin 20 (4)  
for 25 pin(9pin) cables. So unless your software doesn't use the
handshaking lines, conversion between standard and straight through
cables is slightly more complicated, not to mention the fact that you 
need the opposite sex plug.
    Also, I had the impression that the other poster had a nul modem cable
that he needed to convert to standard, but the same applies either way, ie
the handshaking lines and sex of plug make converting more complicated.

See   http://www.megalink.net/~wejones/rs232pin.txt


+----------------------------------+
| Bill Jones, N3JLQ,Sweden, Maine  |
| wejones@megalink.net             |
| http://www.megalink.net/~wejones |
+----------------------------------+
----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home