EIA-232 and RJ45
Phil Toms
Does anybody know which standard (EIA, ISO, CCITT, etc) pertains
to the use of EIA232 on an RJ45 pin connector?
I need to know the standard RJ45 pin-out for EIA 232 signals.
Thanks in advance.
Phil
John Lundgren
states that it must use a 25 pin connector. Period. No exceptions. So
that's why the AT connector on the back of a PC, with a 9-pin connector,
has a pinout that is not even remotely the same as the 25 pin connector.
Also, the RJ-45 connectors have 8 pins, and that may not be enough for a
full asynch connector, which uses 9 or 10 pins. Usually 1 thru 8, and
pin 20, and for modems, pin 22. SO if you want to skimp a little, just
leave off pins 20 and 22, and set the equipment to ignore DTR and Ring.
By the way, much of the ethernet is now using RJ-45 connectors for
10baseT connections from the back of the PC to the hubs. It will be
confusing and possibly detrimental if you use the same connectors on your
serial port equipment. On the other hand, if you have equipment such as
multiplexers that have dozens or hundreds of ports, all using RJ-45, then
you can just use HARMONICAs that the phone co uses on the end of the 25
pair IW cable. It works Ok, and can save a lot on cable costs. It's
also readily available. Best of success.
John Lundgren
specs call for certain wires to be in certain pins. Since the wires are
paired, then the pins are arranged in the same order. The spec for
10baseT connectors is in EIA/TIA 568. It doesn't use the first pair,
because that pair could have a phone circuit on it, which can be 54
volts, or over 100 volts AC when the phone is ringing. The voltage could
burn out network equipment. So pair 2 and 3 are used. Pair 1 is the
white/blue-white wires. Pair 2 is the white/orange-white wires. Pair 3
is the white/green-white wires. Pair 4 is the white/brown-white wires.
I can't tell you which pin they're on, because it depends which spec you
are using: 568a or 568b. We use 568b, or AT&T.
If you intend to use RJ-45 connectors for serial data, which is an
unbalanced signal as used in RS-232, then you must arrange the pins so
that two signals, such as the transmit data and receive data, are NOT on
the two wires of the same pair. There would be severe crosstalk if they
were. Usually, the first pair would have 1 wire grounded and the
transmit data. The second pair would have one wire grounded and receive
data. The third pair would carry the DSR and DTR. The fourth pair would
carry the RTS and CTS. This isn't a very clean way to make cables, but I
guess you get the scenario. Have fun.
Les Reeves
: Does anybody know which standard (EIA, ISO, CCITT, etc) pertains
: to the use of EIA232 on an RJ45 pin connector?
: I need to know the standard RJ45 pin-out for EIA 232 signals.
: Thanks in advance.
I have a box full of standards for RS-232 on RJ45. Each one is the
standard used by whoever built the equipment.
I doubt a real standard has even been proposed. What a shame.
_> Les lre...@crl.com Atlanta,GA
Henry Spencer
>I need to know the standard RJ45 pin-out for EIA 232 signals.
There is none.
Oh, there may possibly be a standard somewhere, defined by someone, but
as far as I know, nobody pays any attention to it. Each manufacturer
makes up his own pinout.
--
"...the Russians are coming, and the | Henry Spencer @ U of Toronto Zoology
launch cartel is worried." - P.Fuhrman | he...@zoo.toronto.edu utzoo!henry
Michel Bissonnette
Sorry to disapoint you guys, but . . .
Yes!, there is an Industry Standard about the RJ-45 pin-out for
RS-232 Serial Communication. You can ask for :
" Use of ANSI/EIA-232-D with 8 position Modular Connector "
Bulletin TSB-25 edited in Feb 89 by the
Electronic Industries Association
1722 Eye Street,N.W. , Washington, D.C. 2006.
It cost about $10.
They suggest 2 configurations depending of the application:
- " Ready-Start " configuration for most of the applications
- " DTE controlled answer " only recommended for Duplex Operation (MODEM)
" Ready-Start " configuration
RJ-45 DB-25
8 positions interface ANSI/EIA-232-D
Circuit Pin # Pin # Circuit Description
107 1 6 CC DCE Ready
109 2 8 CF Received Line Signal Detector
108/2 3 20 CD DTE Ready
102 4 7 AB Signal Ground
104 5 3 BB Received Data
103 6 2 BA Transmitted Data
106 7 5 CB Clear To Send
105 8 4 CA Request To Send
" DTE controlled answer "
RJ-45 DB-25
8 positions interface ANSI/EIA-232-D
Circuit Pin # Pin # Circuit Description
125 1 22 CE Ring Indicator
109 2 8 CF Received Line Signal Detector
108/2 3 20 CD DTE Ready
102 4 7 AB Signal Ground
104 5 3 BB Received Data
103 6 2 BA Transmitted Data
106 7 5 CB Clear To Send
105 8 4 CA Request To Send
As you can see, only pin 1 of the RJ-45 have changed between the 2 configurations
I have also worked with an other RJ-45 connector configuration.
I will describe it only for your information. It will show how painfull it
become when every body " do it own standard " before looking to see if the
industry finally agree on one . May be they have a good reason to do it,
but i am really curious to know it! .... and discusse it !
The other RJ-45 connector configuration is used by XYPLEX on their
16x RS-232 to Ethernet Multiplexer MAXserver 1600
RJ-45 DB-25
8 positions interface ANSI/EIA-232-D
Circuit Pin # Pin # Circuit Description
106 1 5 CB/CE Clear To Send/Ring Indicator
108 2 20 CD DTE Ready
103 3 2 BA Transmitted Data
102 4 7 AB Signal Ground
102 5 7 AB Signal Ground
104 6 3 BB Received Data
106 7 6/8 CC/CF Note1 DCE Ready/Data Carrier Det.
105 8 4 CA Request To Send
Note1
With DCE device, pin7 input is connected to the Device DCD output
With DTE device, pin7 input is connected to the Device DTR output and referred as DSR
( in DECconnect systems the DCD signal is not supported )
The only known advantage of this configuration is that you can easily do a
null-modem cable just by inverting 1 of the connector at one end of the cable.
I Hope all this information is more helpfull than confusing ! . . .
Michel Bissonnette bis...@ireq-sim.hydro.qc.ca
Project Technician
IREQ ( Hydro-Quebec Research Institute )
1800 Montee Ste-Julie, R-213,
Varennes, J3X-1S1, Qc, Canada ( its near Montreal )
Henry Spencer
>There cannot be a EIA 232 standard for RJ45, because the EIA/RS-232
I haven't seen the more recent editions, but my recollection of RS232C
is that it didn't specify a connector or a pinout at all. Those were
defined by other standards.
>that's why the AT connector on the back of a PC, with a 9-pin connector,
>has a pinout that is not even remotely the same as the 25 pin connector.
Uh, I've seen other 9-pin schemes that followed the 25-pin one fairly
closely, within the limited pinout: pins 1-8 the same, pin 9 DTR. The
9-pin pinouts did not arise from adherence to standards; they came about
at the convenience of the manufacturers.
>Also, the RJ-45 connectors have 8 pins, and that may not be enough for a
>full asynch connector, which uses 9 or 10 pins. Usually 1 thru 8, and
>pin 20, and for modems, pin 22. SO if you want to skimp a little, just
>leave off pins 20 and 22, and set the equipment to ignore DTR and Ring.
Leaving off DTR would be pretty stupid. DSR (8) is much more expendable,
since it sees little use in modern equipment. It's also questionable
whether you really need two grounds -- Frame (1) and Signal (7) -- since
they're interconnected at both ends in most equipment anyway. Ground,
RxD and TxD for data, RTS and CTS for handshaking (not what they were
originally meant for, but what they are normally used for now), DTR and
DCD for modem control... 7 pins. For the eighth, several possibilities:
- RI for host-controlled modem answer (rare nowadays)
- DSR if you're obsessed by symmetry
- Frame Ground if you're being picky
- a duplicate Signal Ground, which lets you use the two middle pins for
interconnected grounds, minimizing the fireworks if you accidentally
cross-connect to your phone system
>By the way, much of the ethernet is now using RJ-45 connectors for
>10baseT connections from the back of the PC to the hubs. It will be
>confusing and possibly detrimental if you use the same connectors on your
>serial port equipment...
PCs have connector confusion galore already; a little more isn't going to
make that much difference. Besides, it may be a virtue that you can run
one type of cable with one type of connector and choose RS232 or Ethernet
depending on individual needs.
Henry Spencer
> If you intend to use RJ-45 connectors for serial data, which is an
>unbalanced signal as used in RS-232, then you must arrange the pins so
>that two signals, such as the transmit data and receive data, are NOT on
>the two wires of the same pair. There would be severe crosstalk if they
In practice, at typical RS232 speeds with typical (highly tolerant) RS232
hardware this is nearly a non-issue. For years, we used to use shielded
single-twisted-pair wire for RS232: ground was on the shield, RxD and TxD
were on the twisted pair. (Note, this wasn't my idea and I don't
recommend it!) Some of those wire runs were hundreds of feet long. No
crosstalk problems.
Phil Toms
thanks very much for your informative reply. You
have saved me from many hours of phone drudgery.
As a matter of interest I had called EIA and of course
they denied all knowledge of any such publication.
I now have a little more to go on.
Faith restored in the Net.
thanks again
Phil Toms
Les Reeves
: Michel,
: thanks very much for your informative reply. You
: have saved me from many hours of phone drudgery.
: As a matter of interest I had called EIA and of course
: they denied all knowledge of any such publication.
: I now have a little more to go on.
The EIA standard for a serial non-synchronous interface using 8 position
(RJ-45 type) connector is EIA/TIA-561. It replaces TSB-25.
The document is available for $43.00 from:
Global Eng. Documents, (303) 792-2181
They are the publisher of EIA/TIA standards and specs, and they print an
annual catalog of those documents. The catalog is free (I think).
_> Les
lre...@crl.com Atlanta,GA