The black art. DB-9 male and female pinouts variation
Nisar Jalal
RE: DB-9 male and female pinouts - the black art
I always thought there was only one set of pinouts for RS232 DB-9 plugs.
ie.
1. DCD
2. RD
3. TD
4. DTR
5. GND
6. DSR
7. RTS
8. CTS
9. RI
However, as somebody pointed out to me, pin 3 (Transmit) of a PC
male DB-9 port, needs to connect to pin 2 (Receive) of a peripheral
female DB-9 plug. Connecting pin3 to pin3, would not work.
thereby creating the need for 2 different set of
pinouts for male and female DB-9 plugs.
Perhaps this difference of pinouts is peculiar to PC serial ports?
Could somebody confirm that this theory is correct, and if not, why
not.
If somebody does agree with this, could they please tell me where
to find the 2 different set of pinouts.
Aswell as posting the reply, could you please also send it via e-mail
to me.
Thankyou
John R.Hepburn
Nisar Jalal wrote in message <353C5C...@innocent.com>...
>RE: DB-9 male and female pinouts - the black art
>
>I always thought there was only one set of pinouts for RS232 DB-9 plugs.
>ie.
>However, as somebody pointed out to me, pin 3 (Transmit) of a PC
>male DB-9 port, needs to connect to pin 2 (Receive) of a peripheral
>female DB-9 plug. Connecting pin3 to pin3, would not work.
>
>thereby creating the need for 2 different set of
>pinouts for male and female DB-9 plugs.
>
>Perhaps this difference of pinouts is peculiar to PC serial ports?
>
>Could somebody confirm that this theory is correct, and if not, why
>not.
>
No, talk goes to listen (Tx to Rx) both ways. There would not be much
information passed if no one was listening when someone was talking and visa
versa.The only time 2 is to 2 and 3 is to 3 is if it is an extension cable
but the final ends will still be 2-3 and 3-2.
John R. Hepburn
John's Electronic Services
jhep...@recorder.ca
Dave Baldwin / DIBsed
There is one common 'standard' for PC DB-9 serial ports but that isn't all
there is to it. It would be silly to make a 'standard' PC serial port that
was connected differently, but peripherals aren't all that standard. You
should expect to have to read the manual to find out the connections at the
peripheral end.
TCJ's "Asynchronous Serial Data Communications" page has a couple of PDF
files you might want to look at. One shows common connector pinouts for
serial/telecom cables and another shows wiring for common cables. There is
also serial source code, info on AT commands for modems, and other links
there.
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Reverend Tweek
Nisar Jalal <ni...@innocent.com> wrote:
>
>I always thought there was only one set of pinouts for RS232 DB-9 plugs.
>ie.
>2. RD
>3. TD
>4. DTR
>5. GND
>6. DSR
>7. RTS
>8. CTS
>9. RI
>
>male DB-9 port, needs to connect to pin 2 (Receive) of a peripheral
>female DB-9 plug. Connecting pin3 to pin3, would not work.
Correct. If unit A and unit B were connected 3-3, then both would
be talking and neither listening to what they said. Unit B needs
to HEAR whay unit A says, and Unit A needs to HEAR what unit B says.
>thereby creating the need for 2 different set of
>pinouts for male and female DB-9 plugs.
Oh, and actually, at least with the original DB-25 RS-232c quasi-format,
there *are* two formats... DCE for Data Communications Equipment such
as modems, and DTE for Data Terminal Equipment such as terminals.
[RS-232C doesn't really specify pinouts, just voltages and control lines]
On DTE equipment, pin 2 is TXD and pin 3 is RXD while on DCE it is
the reverse of that. Besides those signals being switched, the
handshaking lines are also paired with their appropriate communications
partner when connecting between DCE and DTE equipment. When connecting
between these two types of equipment, a straight-thru cable will work.
Ont the other hand, if you are connecting two pieces of equipment together
which use the same data equipment designation (two terminals or two
communications) you will have to cross the lines so that TXD goes to RXD,
RXD to TXD, as well as crossing the handshaking lines since the pin
designations are NOT complimentary on similar type equopment.
>Perhaps this difference of pinouts is peculiar to PC serial ports?
It's peculiar to ANYTHING where communications is required. You don't
talk into someone's mouth... you talk into their ear. They don't
listen to you on their telephone mouthpiece because you are talking
into the mouthpiece on your end... however, the industry has tried
to make it simple by designating DTE and DCE formats, so that all
you need is a straight cable... and it would work fine in cases where
you are connecting a computer to a modem... but if you want to connect
two computers to each other without a modem, or if you want to connect
two modems back to back, then you can't use a straight-thru cable.
In the case of your palm computer, (and this is strictly theory, I
ahve no idea as to its specs) they could make the serial port on
it so that you could either attach it to a computer with ease, or
to a periphrial with ease... Do they treat the design of the palm
computer as Data Terminal Equipment, or as Data Communications Equipment?
It's DTE when used by itself or with a printer or modem, but when it
connects to a computer, is it the computer's peer, or a periphrial of
the computer? They had to make a decision somewhere along the line
as to whether to make it DTE or DCE, and whichever they made it to
be, you then have to flip lines when communicating with like devices.
>Could somebody confirm that this theory is correct, and if not, why
>not.
See above.
>If somebody does agree with this, could they please tell me where
>to find the 2 different set of pinouts.
Any good "Serial Communications" book in your library should have it.
A good quality modem manual might even give you a considerable amount
of information on this.
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Ag@whd
On Tue, 21 Apr 1998 15:56:36 GMT, tw...@netcom-NO.SPAM-com (Reverend
Tweek) wrote:
It's really very simple.
When IBM changed from a 25W 'D' to a 9W 'D' they exchanged the TX and
RX pin designations on the 9W from whath they were on the 25W.
With either 9W or 25W you still have the issue of whether one unit or
the other is either DCE or DTE.
If you have two units both with 25W connectors (or both with 9W
connectors) and one is DCE and the other is DTE then you can connect
the one directly pin for pin to the other.
This is because the DTE device transmits on TX and the DCE device
listens on it's 'TX' (i.e. it really receives on it).
If you have two DTE devices (say two PC's talking to each other) and
both have a 25W or both have a 9W then you need to swap the TX and RX
lines (and often other handshaking lines too) because they are both
the same class of equipment.
The fun starts when they are still both DTE but one has a 25W and the
other has a 9W. This time pin 2 goes to pin 2, and pin 3 goes to pin
3. At first sight it doesn't seem as if you have the required "turn
around", but in fact you do - because the pin designations were
exchanged (i.e. are different) for 9W and 25W D connectors.
When you have a PC with a 9W D (a DTE device) connected to a modem (a
DCE device) with a 25W D, then you need pin 2 connected to pin 3 and
vice versa.
Confused?
No?
Then I haven't explained it right!
Adrian
WWW WWW Adrian Gothard
WWW ww WWW White Horse Design
WWWWWWWWWW
WWWW WWWW w...@zetnet.co.uk, http://www.users.zetnet.co.uk/whd
---
Designers of GPS-based satellite tracking systems for vehicles
Lord Garth
The function seems confusing only because you are connecting a
Data Terminal Equipment (DTE) to another Data Terminal Equipment
device.
This not actually supposed to be the case, DTE was meant to plug
directly into DCE or Data Communication Equipment. Witness the
fact that a PC 25 pin DTE port plugs directly into an external
modem DCE port with NO crossover wires. This situation was
blurred by the introduction of the 9 pin "AT" port.
Add to this the fact that manufacturers tended to use whatever they
liked for hardware handshaking. I have seen the following pins used
for hardware flow control:
11, 14, 18, 19, 20
Jon
Al Savage
On Tue, 21 Apr 1998 20:47:14, h...@approve.se.NO_JUNK_EMAIL (Goran
Larsson) wrote:
> +--------- D-shell
> |
> |+-------- shell size
> ||
> || ++----- number of pins
> || ||
> VV VV
> DA 15 AUI
> DB 25 RS-232
> DC 37 RS-422
> DD 50 old SCSI (Old Sun and Digital)
> DE 9 small RS-232
> DE 15 new VGA connector
Can anyone else verify this? Or point to a reference?
Regards,
Al
asa...@iname.com (email) asa...@cio.net (files > 2mb)
Reed Park
John R.Hepburn wrote:
> Nisar Jalal wrote in message <353C5C...@innocent.com>...
> >RE: DB-9 male and female pinouts - the black art
> >
> >I always thought there was only one set of pinouts for RS232 DB-9 plugs.
> >ie.
The DB-9 connector should never be refered to as "RS232" as the
RecommendedStandard # 232 is very specific, and states that the connector is 25
pins. It doesn't
even say it has to be a DB25 connector, it just states it is 25 pins.
Sorry to be real picky, but lets not change the standards simply because
"everybody
calls it that"
The nice thing about standards, is, that there are so many to choose from.
Regards
Reed
> >However, as somebody pointed out to me, pin 3 (Transmit) of a PC
> >male DB-9 port, needs to connect to pin 2 (Receive) of a peripheral
> >female DB-9 plug. Connecting pin3 to pin3, would not work.
> >
> >thereby creating the need for 2 different set of
> >pinouts for male and female DB-9 plugs.
> >
> >Perhaps this difference of pinouts is peculiar to PC serial ports?
> >
> >Could somebody confirm that this theory is correct, and if not, why
> >not.
> >
>
John R.Hepburn
>The DB-9 connector should never be refered to as "RS232" as the
>RecommendedStandard # 232 is very specific, and states that the connector
is 25
>pins. It doesn't
>even say it has to be a DB25 connector, it just states it is 25 pins.
>
>Sorry to be real picky, but lets not change the standards simply because
>"everybody
>calls it that"
>
>The nice thing about standards, is, that there are so many to choose from.
>
>Regards
>Reed
No arguement Reed. I must admit though I have given up asking manufacturers
what the standard is on their specific units. I now talk in their language
and say "I know it is standard 232... but what connector and which pins are
you using". I even had one piece of equipment which had 3 screw connections
and was labeled rs-232 com. It seems anymore they have limited this
designation to refer to the electrical type and protocol of communication
rather than any external physical standard.
It may be wrong, but if everyone is doing it (in different ways), then by
definition it is 'normal' , which is a half step away from 'standard'.
I agree with you !00%, but have put up the white flag on this issue years
ago.
Robert Blackshaw
Reed Park <reed...@nbnet.nb.ca> wrote:
<snip>
>The DB-9 connector should never be refered to as "RS232" as the
>RecommendedStandard # 232 is very specific, and states that the connector is 25
>pins. It doesn't
>even say it has to be a DB25 connector, it just states it is 25 pins.
>Sorry to be real picky, but lets not change the standards simply because
>"everybody
>calls it that"
With more than 20 years in the standards arena may I be a little
picky and note that it is now EIA_232-D. The old RS designations
are a thing of the past.
Bob
Gary Tait
In article <TPu4qbPdipCY-pn2-lr8vDyB8bpbu@localhost>, asa...@iname.com wrote:
#On Tue, 21 Apr 1998 20:47:14, h...@approve.se.NO_JUNK_EMAIL (Goran
#Larsson) wrote:
#
#> +--------- D-shell
#> |
#> |+-------- shell size
#> ||
#> || ++----- number of pins
#> || ||
#> VV VV
#> DA 15 AUI
#> DB 25 RS-232
#> DC 37 RS-422
#> DD 50 old SCSI (Old Sun and Digital)
#> DE 9 small RS-232
#> DE 15 new VGA connector
#
#Can anyone else verify this? Or point to a reference?
#
#Regards,
#Al
#
#asa...@iname.com (email) asa...@cio.net (files > 2mb)
That is true. I have a big thick Electrosonic catalogue,and various
manufacturers list their D-Sub compunents like that.
I guess ,since home computers,started out with DB25 serial ports,the DB stuck
(or the general public didn't know of DA,DC,DD,DE).
Gary Tait,VE3VBF
Dave Baldwin / DIBsed
According to AN-917 from National Semi, the DB-9 serial connector is
specified in EIA/TIA-574. And the current 'RS-232' standard is
EIA/TIA-232F. You can get a copy of AN-917 in PDF format from National or
from TCJ's "Asynchronous Serial Data Communications" page. It covers many
of the 'standard' connector pin-outs used in telecommunications.
Andrew Dyer
In article <356bceae...@znews.zetnet.co.uk>,
>Confused?
>No?
>Then I haven't explained it right!
>
You neglected the also fun issue of getting the footprint right if you
are designing a PCB with DB-9 or DB-25 connectors. For many moons our
PCB gurus decided that only one footprint was needed for either a male
or female connector - it was up to the designer to remember to get the
pins switched around if you are using the "wrong" sex connector :-)
--
| Andrew Dyer <ad...@midway.com> or <ad...@mcs.net> |
| Sr. Design Engineer (773) 961-1751 |
| Midway Games, Inc. (773) 961-1890 (fax) |
| 2727 W. Roscoe Ave., Chicago, IL 60618 |
W. Kranitz
Ag@whd wrote in message <356bceae...@znews.zetnet.co.uk>...
>On Tue, 21 Apr 1998 15:56:36 GMT, tw...@netcom-NO.SPAM-com (Reverend
>Tweek) wrote:
>
>both have a 25W or both have a 9W then you need to swap the TX and RX
>lines (and often other handshaking lines too) because they are both
>the same class of equipment.
>
This is what's refered to as a NULL modem cable...
Wes
Sandy
Though my question is somehow related to DB-9 it perhaps does not fit
in here exactly. Still I wish someone out there will give me the
following info:
Motherboards now come with integral serial ports and we have 10 pin
headers on the motherboard. A flat ribbon cable connects this to the
DB-9 socket on the back of the cabinet.
1) What are the signals on the 10 pin header?
2) Are the pins 2 and 3 connected straight through or crossed?
Sandy
(Remove the dot after the mr for e-mail)
Tom MacIntyre
To the best of my knowledge, pins 2 and 3 are connected straight
through. Another aspect to this - some DB-9 adapter cables have the
pins numbered 1 2 3 4 5
6 7 8 9 10
and some are 1 3 5 7 9
2 4 6 8 10
(This is, of course, at the opposite end to the DB-9.) If you ever get
an adapter that won't work for seemingly no reason, that's probably
it.
Niall
On Tue, 28 Apr 1998 01:10:02 GMT, mr.s...@poboxes.com (Sandy) wrote:
>Though my question is somehow related to DB-9 it perhaps does not fit
>in here exactly. Still I wish someone out there will give me the
>following info:
>
>Motherboards now come with integral serial ports and we have 10 pin
>headers on the motherboard. A flat ribbon cable connects this to the
>DB-9 socket on the back of the cabinet.
>
>1) What are the signals on the 10 pin header?
>
>2) Are the pins 2 and 3 connected straight through or crossed?
>
There are at least 2 standards for motherboard serial headers. This
does not seem to be widely known, but can cause untold hassle trying
to get a mouse to work. I always now use the cable which was supplied
with the motherboard, even though it means more work when swapping a
motherboard.
Niall
Gary Tait
In article <3543ce5a...@news.vsnl.net.in>, mr.s...@poboxes.com (Sandy) wrote:
#Though my question is somehow related to DB-9 it perhaps does not fit
#in here exactly. Still I wish someone out there will give me the
#following info:
#
#Motherboards now come with integral serial ports and we have 10 pin
#headers on the motherboard. A flat ribbon cable connects this to the
#DB-9 socket on the back of the cabinet.
#
#1) What are the signals on the 10 pin header?
#
#2) Are the pins 2 and 3 connected straight through or crossed?
#
#
#Sandy
#(Remove the dot after the mr for e-mail)
#
#http://members.tripod.com/~diligent
There are basically 2 standards. In my diagram ,you are looking down to the
pins on the motherboard,and the numbers represent the pins on the DE9 male.
Type I
6 7 8 9
1 2 3 4 5
Type II
2 4 6 8
1 3 5 7 9
At quick glance ,you can tell if your board is a type I or II by seeing
if the pin connected to ground is in the end(type I),or the middle (type II).
Gary Tait,VE3VBF
D. Roman
>
> 1) What are the signals on the 10 pin header?
>
> 2) Are the pins 2 and 3 connected straight through or crossed?
>
>
> Sandy
> (Remove the dot after the mr for e-mail)
>
> http://members.tripod.com/~diligent
I'm not sure if the ribbon cable connects to the DB-9 in pin order...but
you can use an Ohm meter to see if pin one on the DB-9 is attached to pin
1 on the Ribbon Cable connector and the same for the rest of the pins.
The signals on the DB-9 for an RS-232 on the IBM PC are:
___
1 - Data carrier detect (DCD) low-logic true
2 - Recieved Data (RxD)
3 - Transmitted data (TxD)
4 - Data terminal ready (DTR)
5 - Signal ground (GND)
_____
6 - Data set ready (DSR) low-logic true
____
7 - Request to send (RTS) low -logic true
____
8 - Clear to send (CTS) low-logic true
9 - Ring indicator (RI)
Hope this helps.......... Oh! 2&3 are reversed outside of the computer
- like in a null modem cable.......not on the inside :)
Naresh
Usually for Pins 2 and 3 , they are not crossed unless you intend to
communicate with other devices.
By the way, I have a great chip, which I like to share:
8-Bit Parallel Output Addressable Serial-to-Parallel Converter
The MNT-101 series preprogrammed microcontrollers
were designed to perform high-speed serial-to-parallel
conversion from a standard RS-232 data source. Baud
rate is determined by the speed of the ceramic resonator or
crystal attached to the microcontroller. (4Mhz suppllied)
Up to 7 MNT-101 can be attached to a single RS-232 serial
port providing a total 56 individually addressable
output bits. The NAME jumpers N1, N2, and N3 deter-mine
its address on the serial port. When all name jumpers
are installed, the MNT-101 performs a raw serial-to-parallel
conversion. In turn the output bit could be connected to a switching
relay, Solid state relay or triac to power on or off any electronic or
electrical device.
The system uses two wires from the Com port and it can run upto a mile.
Please let me know if you are intrested in this chip.
Thank you
Naresh