'What RJ-11 pin assignment used for RS-232?'
Is there a standard or preferred pin assignment when a RJ-11 connector is
used for a RS-232 connection? Also, how are the pins numbered?
Thanks for any help.
|I probably should keep my mouth shut since I'm not an expert <g>, but I'm
not aware of a standard per se for RJ-11. Normal phone connections start
at the center two pins and work their way out for each line.
Are you designing a board that will use an RJ-11 connector or are you
wanting to make a cable for an existing RJ-11 connector ? If the former, I
would suggest using the same pin 1 as RJ-45. That is, turn the connector
upside down with the latching lever on the bottm looking at the recessed
gold contacts. Pin 1 is on the left :
| Pin 1
| | | | | |
As far as a perferred pin-out, hopefully someone here can tell you whether
it matters. I wouldn't think it does. I too would be interested in that
information as I also have a project that I want to use an RJ-11 for RS232.
On Friday, June 04, 1999 6:57 AM, Jerome Knapp
[SMTP:SKCLA.MONSANTO.COM] wrote: jjknap
> Is there a standard or preferred pin assignment when a RJ-11 connector
> used for a RS-232 connection? Also, how are the pins numbered?
> Thanks for any help.
> Jerome Knapp.
Marco DI LEO
I also know of no standard for wiring these, but I'd sure like to
see some symmetry in the wiring. Starting at one end, we might go:
Otta put DCD in there somewhere... Anyway, if all RJ11 connectors
were wired like this, or something similar, there would be no need for a
distinction between DTE and DCE. We'd always use a "cross over cable"
and everything would always work.
Hallikainen & Friends, Inc.
See the FCC Rules at http://hallikainen.com/FccRules and comments filed
in LPFM proceeding at http://hallikainen.com/lpfm
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|On Fri, Jun 04, 1999 at 09:16:45AM -0500, Eric Oliver wrote:
> I probably should keep my mouth shut since I'm not an expert <g>, but I'm
> not aware of a standard per se for RJ-11. Normal phone connections start
> at the center two pins and work their way out for each line.
I have been working with these kinds of things for many
years and have never noted a "standard" for RS-232. It
makes very little difference in reality, and it seems
that everyone just makes something up, so you have little
hope of minimizing compatiblity issues. The only concern
would be if one had to mate with an existing device, in
which case you would probably want to pick a pinning
that would allow you to use a straight-through cable
to the other unit (swap your TX & RX pins, if necessary,
on the device side of the RJ-11 jack, not inside the patch
cable); then you can use any old standard off-the-shelf
RJ11 patch cables.
If you have an RS-422 interface, then the pinning and
the patch cable can become more of a concern, because
for optimal performance you'd like the TX+ and TX- on one
twisted pair and the RX- and the RX+ on another.
Bob Drzyzgula It's not a problem
drzyzgula.org until something bad happens bob
William Chops Westfield
There is no standard for rs232 over rj11 or rj45 (8 pins.)
standards that are convenient at the jack tend to result in inappropriate
pairing of signals in building wiring (there ARE standards for which
rj11/rj45 pins go in which pairs...)
cisco uses something like DSR CTS RD GND GND TX RTS DTR which has the useful
property (?) of changing DTE/DCE-ness when you flip the cable over, and of
allowing "smaller" cables to achieve smaller functionality. (I might have
DSR/CTS and RTS/DTR reversed.) Customers have complained about the
resulting pairing, though. (we shamelessly copied the center 6 pins from
a common DEC terminal server scheme, just before they changed it, I think.)
|> Is there a standard or preferred pin assignment when a RJ-11
> connector is used for a RS-232 connection?
Each vendor assigns the RS-232 functions to RJ11 or RJ45 pins
as they see fit. I know of no standard.
I personally prefer DEC's MMJ (modified modular jack) style.
This is what BillW from Cisco mentioned. From my notes, I
belive the pinout is:
pin 1 = data terminal ready (DTR)
pin 2 = transmit data (TxD)
pin 3 = transmiter ground
pin 4 = receiver ground
pin 5 = receive data (RxD)
pin 6 = data set ready (DSR)
A neat feature is that is dispenses with RS-232's (EIA-232's)
DTE versus DCE handed-ness. A normal flat cable would hook up
any two units since it automatically swapped the pins (pin 1
on one end becomes pin 6 on the other end, etc).
DEC actually used RS-423. It was compatible with RS-232 when
you tied MMJ pins 3 & 4 to the RS-232 side's signal ground. I
think this same pinout would work well for RS-232 on RJ11s.
> Also, how are the pins numbered?
Looking at the face of the jack with latch at the bottom, pins
are numbered 1 to 6 from left to right. See drawing:
RJ11: 1 2 3 4 5 6
! I I I I I I !
! I I I I I I !
Also note that large numbers of RJ11 plugs and cables only
provide conductors for the 4 middle positions (pins 2 to 5).
RJ45 has 8 conductors. Pins are numbered the same with top
left corner being pin 1. If you insert an RJ11 plug in an
RJ45 jack, the RJ11's 6 positions mate with RJ45 pins 2 to 7.
Jones Computer Communications frumble.claremont.edulee
509 Black Hills Dr, Claremont, CA 91711 voice: 909-621-9008
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