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The Complete pinouts guide to
Parallel-Serial Port, Network and Monitor Cables

Everything for DCC (Direct Cable Connection of Win95/98), Normal and Null Modem Cables, etc.

INDEX of Chapters
1. Preface
2. IBM Basic concepts of Computer Cabling.
3. IBM DB-25 and DB-9 diagrams.
4. IBM DB-25 and DB-9 numbering scheme.
5. IBM Serial port Pin Descriptions (Wire name) for each pin number.
6A.IBM Parallel port Pin Descriptions (Wire name) for each pin number.
  6B.IOMEGA ZIP DRIVE Parallel port Pinouts.
7A.IBM Parallel Port Laplink Cable Pinout.(for DCC of WIN9x.)
  7B.Serial Port Null-modem Cable (for DCC of WIN9x.)
8. IBM Null-Modem pinouts. (DB-25 to DB-25), (DB-9 to DB-9) and (DB-25 to DB-9).
9. IBM Normal Modem (Cable) pinouts. (DB-25 to DB-25) and (DB-25 to DB-9).
10. The pin-configuration of Internal Serial Cables inside Cabinet.
12. Other links
13. WARNING
    

1. PREFACE

Here are several diagrams and tables explaining parallel port, serial port and null-modem
configurations, which are mostly available on Internet. I was forced to provide this information on
the Internet by myself when my search began for getting Laplink Cable or Null Modem Cable to
transfer data from one Win95 PC to another Win95 PC in Sept-97. I bought the laplink cable in the
market and that served my purpose as I successfully transferred data from "HOST" to "GUEST"
computer with Laplink. But also I was bit worried with the cost of LAPLINK cables available in the
market as I purchased it at at least thrice the cost of its material cost. Let's discuss this in Indian
Rupees. I purchased Laplink cable at Rs.120/- in the market. But the material cost I calculated was
only Rs.50/- if we prepare this at home if you have a logically working BRAIN and a little bit
knowledge of soldering wires, which most of us do while repairing toys or portable radios. So I did
opened the D-25 Female pins of my Laplink cable and studied the colour combinations of wires and
prepared the following PINOUT Chart for those who want to make LAPLINK Cable at home. (THIS IS
JUST AN INFO PAGE, BUT PLEASE USE THIS INFO AT YOUR OWN RISK.)

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2. BASIC CONCEPTS OF COMPUTER CABLING

A PARALLEL port can consist of only 25 pin port adapter called a DB-25 and a serial port can consist of either a 25 pin port adapter called a DB-25 or 9 pin adapter called a DB-9 port adapter. Whether the port is a 9 pin or 25 pin it can accomplish all of the same tasks that serial port communications have been designed for.

Each adapter can be a male type connector with pins or a female type adapter with tiny holes.
Generally a PRINTER port (called LPT1) on the back of a computer is female type adapter and we need to use MALE DB-25 pin cable on it for PRINTER connection or for parrallel LAPLINK cable.

And a COM port on the back of a computer is male for the serial ports but it may not necessarily be. Below are diagrams of a DB-25 and DB-9.

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3. IBM DB-25 and DB-9 diagrams.

(Each diagram on this page is the view you see when you look into the end of the cable from the
outside of the cable.)

The "o" characters represent holes, the "." characters represent pins.
A DB-25 looks like this...

Diagram #1
Female:                        Male:
_____________________________  _____________________________
\ o o o o o o o o o o o o o /  \ . . . . . . . . . . . . . /
 \ o o o o o o o o o o o o /    \ . . . . . . . . . . . . /
  -------------------------      -------------------------

And a DB-9 is like this...

Diagram #2
Female:        Male:
_____________  _____________
\ o o o o o /  \ . . . . . /
 \ o o o o /    \ . . . . /
  ---------      ---------

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4. IBM DB-25 and DB-9 numbering scheme. (Pin numbers)

Each pin has a number assigned to it. When connecting null modem, for example, it is important to know these numbers in order to select the correct cables, or when making your own cables.

DB-25 Connector
Chart #1 (Female)
  13              <------- 1
 _____________________________
 \ o o o o o o o o o o o o o /
  \ o o o o o o o o o o o o /
   -------------------------
    25             <----- 14
  
Chart #2 (Male)
  1 ------->              13
 _____________________________
 \ . . . . . . . . . . . . . /
  \ . . . . . . . . . . . . /
   -------------------------
   14 ----->             25 
DB-9 Connector
Chart #3 (Female)
   5 4 3 2 1
 _____________
 \ o o o o o /
  \ o o o o /
   ---------
    9 8 7 6     
Chart #4 (Male)
   1 2 3 4 5
 _____________
 \ . . . . . /
  \ . . . . /
   ---------
    6 7 8 9    

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5. IBM Serial port Pin Descriptions (Wire name) for each pin number.

For following all connections we may use these chart for transmission of Data via Serial Port.
Chart#11
Pin assignments
DB-25
2 TD Transmit Data
3 RD Receive Data
4 RTS Request to send
5 CTS Clear to send
6 DSR Data Set Ready
7 SG Signal Ground
8 DCD Data Carrier Detect
20 DTR Data Terminal Ready
22 Ring Ring Indicator
Chart#12
Pin Assignments
DB-9
1 DCD Data Carrier Detect
2 RD Receive Data
3 TD Transmit Data
4 DTR Data Terminal Ready
5 SG Signal Ground
6 DSR Data Set Ready
7 RTS Request to Send
8 CTS Clear to Send
9 Ring Ring Indicator
IMP. NOTE : In DB-25 serial cable following numbered pins are NOT USED. They are 1, 9, 10, 11, 12,
13, 14, 15, 16, 17, 18, 19, 21, 23, 24 and 25.

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6A. IBM Parallel port Pin Descriptions (Wire name) for each pin number.

Hi there, as far as I am concerned it is very difficult to make your own printer cable and anyways
they are cheap and easy to find in a store down there on the street. REMEMBER I AM NOT ANY
TECHNO-WIZARD. So don't ask me details of each pins. You can email your problems regarding this
section to the author of the chart mentioned below. But, I am giving the collection of data
transmission of most common cables for everybody's reference. Following is the chart for
transmission of Data via Parallel Port.

Chart#13
Pin Assignments of Parallel Port (LPT1)
Female DB-25 on PC
<= in
or
=> out
DB25
Pin
Cent
Pin
Name of
Signal
Reg
Bit
Function Notes
=> out 1 1 -Strobe C0- Set Low p1ulse >0.5 us to send
=> out 2 2 Data 0 D0 Set to least significant data
=> out 3 3 Data 1 D1 ...
=> out 4 4 Data 2 D2 ...
=> out 5 5 Data 3 D3 ...
=> out 6 6 Data 4 D4 ...
=> out 7 7 Data 5 D5 ...
=> out 8 8 Data 6 D6 ...
=> out 9 9 Data 7 D7 Set to most significant data
<= in 10 10 -Ack S6+ IRQ; Low Pulse ~ 5 uS, after accept
<= in 11 11 +Busy S7- High for Busy/Offline/Error
<= in 12 12 +PaperEnd S5+ High for out of paper
<= in 13 13 +SelectIn S4+ High for printer selected
=> out 14 14 -AutoFd C1- Set Low to autofeed one line
<= in 15 32 -Error S3+ Low for Error/Offline/PaperEnd
=> out 16 31 -Init C2+ Set Low pulse > 50uS to init
=> out 17 36 -Select C3- Set Low to select printer
== 18-25 19-30,
33,17,16
Ground - Do not connect any of these grounds to a shield

Imp. Note:
Some cables, ports, or connectors may not connect all grounds. Centronics pins 19-30 and 33 are "twisted pair return" grounds, while 17 is "chassis ground" and 16 is "logic ground".

"<= In" and "=> Out" are defined from the viewpoint of the PC, not the printer. The IRQ line (-Ack/S6+) is positive edge triggered, but only enabled if C4 is 1.


6B. IOMEGA ZIP DRIVE Parallel Port Cable Pinouts
(Straight-through PP Cable)

Most of the The External Parallel Port devices like IOMEGA ZIPDRIVE uses Straight-through Parallel Port cable with Straight pinouts like 1 to 1, 2 to 2, 3 to 3 and so on upto 25 to 25. Though I may not be sure about other Parallel Port Devices like External CDROM drives, you can give it a try for other units on your own risk.

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7A. Parallel Port Laplink Cable Pinout

Laplink cable is used to link two PCs with MSDOS 6.0 or later, very effectievly by using INTERSVR.EXE (on Host) and INTERLNK.EXE (on GUEST) PCs.

Laplink cable is also successfully used by me to link two PCs for only FILE TRANSFER (not playing Games), with WIN95 and Direct Cable Connection program with common protocol as "NETBEUI" on both Computer´s Network Section of Control Panel. In Network section you must have installed "Client for Microsoft Networks", "File and Printer Sharing for Microsoft Networks" and one more protocol other than TCP/IP, that is "NetBEUI". Both the options in "File and Print Sharing" button should be selected (checked) to allow all users to access files and printer.

Then one computer must be as HOST mode and the other should be as GUEST mode. Also only two computers can be connected to each other for only FILE TRANSFER and not for anything else. The Rest is explained in HELP and Troubleshooting Section of WIN95 itself. PLEASE DO NOT EMAIL FOR THE DCC OF WIN95/98 FOR THIS, BELIEVE ME YOU WILL FIND THE BETTER INFO IN HELP OF WIN9x or try my FAQ page for more info.

If you are seeking to buy a Parralel port Laplink cable, or trying to make your own cable, you should know what pins need to be switched in order to make it. Below is a chart of what pins go to what on the other end. Only 18 pins are used in a Laplink Cable, therefore I will only show those eighteen here.

To make this cable we need
1. TWO numbers of DB-25 Male Sockets.
2. Shielded Cable with 18 cores (lines of wires).

Chart#5
DCC Parallel Laplink Cable Pinouts.
Male DB-25 ==>> Male DB-25
1 Both Not used
2 to 15
3 to 13
4 to 12
5 to 10
6 to 11
7 Both Not used
8 Both Not used
9 Both Not used
10 to 5
11 to 6
12 to 4
13 to 3
14 Both Not used
15 to 2
16 Both Not used
17 to 19
18 to 18
19 to 17
20 Both Not used
21 to 21
22 to 22
23 to 23
24 Both Not used
25 to 25
Pinbody* to Pinbody
* = In my cable one wire was attached to the metal body of the Male pins on both sides. Total 18
wired cable is necessary for this cable including one wire for Body of the pin too.

SPEED: Parralel port Laplink cable is always faster than Serial port Cable because of more numbers of cores of wires used in Parallel port cable (25 pin) than Serial port Cable (9 pins). The expected speed is 300kb/second but it is extremely dependent on the different quality chipset structure of Parallel Ports on different makes of the Motherboards. Some even reported me the lowest speed of 60kb/sec even though all other settings are correct. Its recommended that you setup LPT1 mode as only "ECP/EPP" or "ECP" mode in bios to get better speed, and not the "Normal" (4bit/8bit) modes.

 

7B. NULL-MODEM cable for DCC file transfer?

Yes! About a DCC of Win9x thru Serial Port a very important information I am going to put over. Please read carefully. We can also use Null-modem cable to use with DCC for Data transfer on Serial port with all above settings identical as we use for DCC with Laplink Cable on Printer Port. The source of the info is http://www.kime.net/directcc/directcc95.htm. Please do not get confused with DTE and DCE descriptions on that site as DTE is DB9 or DB25 MALE pin as found on system and DCE is DB9 or DB25 Female socket/pin as found on Modems. We usually get MALE DB9 or DB25 pin serial ports on our computers which can also be called DTE type port. So, just Enjoy. Next section is how to build your own Null-Modem cable.

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8. IBM Null-Modem pinouts. (DB-25 to DB-25), (DB-9 to DB-9) and (DB-25 to DB-9).

For making Null modem cable following is a chart of pinout. Only 8 pins are used in a null modem, though there are 25 pins on DB-25 socket. You need 8 or 9-wired cable with two DB-25-Female pin socket or DB-9-Female pin socket or one of both.

IMPORTANT : Both pin sockets must be of FEMALE type. This may not be applicable on some machines, so please check your serial ports of both the machines as there must be MALE pins at back of your both computers.

Chart #6
Chart #7
Chart #8
Null-Modem Pinouts
DB-25 to DB-25
2 to 3
3 to 2
4 to 5
5 to 4
6 and 8 to 20
7 to 7
20 to 6 and 8
Null-Modem Pinouts
DB-9 to DB-9
1 and 6 to 4
2 to 3
3 to 2
4 to 1 and 6
5 to 5
7 to 8
8 to 7
Null-Modem Pinouts
DB-25 to DB-9
2 to 2
3 to 3
4 to 8
5 to 7
6 and 8 to 4
7 to 5
20 to 6 and 1

Now why this cable is called null modem without using the modem?

by grimace (grimace@xnet.com) That's good question. But if you think a little bit, you will get an
answer that as we don't use modem and use modem-like connection on two computers staying
together, so we call it Null-Modem Connection.

Most important is, as you may know that modem have its own data-transmission method and special combination of the data input-output is required to be configured to each pin of the modem cable so the special modem to computer cable is used. But if you give more attention on CHART#11 and CHART#12 of my page you will get an idea that how actual the DATA-TRANSMISSION takes place. Now if we want to play multiplayer game from remote areas we need to connect systems with MODEMS as follows...

MODEM GAME PLAY
A's Computer ###### A's MODEM ------> TELEPHONE CO.----->B's MODEM ###### B's Computer

In above (1st) diagram '######' is the cable which connects the Computer to MODEM. The one which comes with modem.

NULL MODEM GAME PLAY
A's Computer =================== B's Computer

In this (2nd) diagram '===========' resembles the null modem cable emulating the 1st transmission. Now in above method the Null modem Cable's pinouts are adjusted in such a way that it emulates the modem connection to the same DATA-TRANSMISSION as MODEM to Computer connection requires. See chart#9 and #10. Therefore it is called Null-Modem cable. Hope I could explain you the whole saga. <phew>

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9. IBM Normal-Modem Cable pinouts. (DB-25 to DB-25) and (DB-25 to DB-9).

IMPORTANT : Both pin sockets must be of DIFFERNT type. This means that for modem-side of cable we need to use MALE type of DB-25 pin. And on CPU side of cable we need to use FEMALE type of DB-25 or DB-9 pin.

Chart #9
Chart #10
Normal-Modem Pinouts
DB-25 to DB-25
2 to 2
3 to 3
4 to 4
5 to 5
6 to 6
7 to 7
8 to 8
20 to 20
22 to 22
PinBody* to Pinbody*
Normal-Modem Pinouts
DB-25 to DB-9
2 to 3
3 to 2
4 to 7
5 to 8
6 to 6
7 to 5
8 to 1
20 to 4
22 to 9
PinBody* to Pinbody*
* Pinbody is OPTIONAL. We easily get cable with 9-wires in it, but not 10 then Pinbody can be
attached with shielded wire. The one which I examined from a reputed company was having body
of pins connected with shileded wire (let's assume earthing line.)

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10.The pin-configuration of Internal Serial Port Cables inside Cabinet.

The pin-configuration of internal serial cables (the one that connects from the motherboard to the
case) are different for different motherboards, which come in two types. One with straight pins as
in old mobos like 286/386/486. And another is twisted style cable like in latest pentiums. The MALE
DB9 pin is connected to serial port on motherboard with 9 wired cable in following two types. Both
Serial ports on motherboard have 10 wires but only 9 of them to connect to MALE DB9 Serial Pins.
Please do not connect 10th core anywhere.
Chart# 14
DB9 Pinouts of
STRAIGHT SERIAL PORT
on 286/386 systems
Cable Wire number
on motherboard
Wire Connected
to male DB9 pin
on cabinet.
1 Red Wire 1
2 2
3 3
4 4
5 5
6 6
7 7
8 8
9 9
Chart# 15
DB9 Pinouts of
TWISTED TYPE SERIAL PORT
on modern systems
Cable Wire number
on motherboard
Wire Connected
to male DB9 pin
on cabinet.
1 Red Wire 1
2 6
3 2
4 7
5 3
6 8
7 4
8 9
9 5

The MALE DB-25 pin is connected to serial port on motherboard with 9 wired cable (Yes, 9-wired cable) in following two types. Both Serial ports on motherboard have 10 wires to connect to MALE DB25 Serial Pins as follows. Take it.
Chart# 16
DB25 Pinouts of
STRAIGHT SERIAL PORT
on 286/386 systems
Cable Wire number
on motherboard
Wire Connected
to male DB25 pin
on cabinet.
1 Red Wire 8
2 3
3 2
4 20
5 7
6 6
7 4
8 5
9 22
Chart# 17
DB25 Pinouts of
TWISTED TYPE SERIAL PORT
on modern systems
Cable Wire number
on motherboard
Wire Connected
to male DB25 pin
on cabinet.
1 Red Wire 8
2 6
3 3
4 4
5 2
6 5
7 20
8 22
9 7
NOTE: The 10th Core Wire from motherboard is an Optional line which can be connected to pin 1 of
DB25 with no harm.

IMP: Above are the exact pinouts of the all four types of working serial ports with me for IBM Machines. Believe me, they should work. Please see Chart#11 and Chart#12 in Section 5 of this page for pin-Descriptions of DB9 and DB25 Serial ports.

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11. Other Links

Help on Direct Cable Connection in Win95 by Acclaim@geocities.com

Apple Mac users guide on Modem Pinouts by RADICAL Systems

Date: wed, 24 Sep 1997 19:51:38 +0100 From: "Jesse Eissens" (jeissens@bigfoot.com)
To: (mahendra@geocities.com) CONTENT : Whould you happen to have the pinout for a 15 pin monitor connector? I have a Compaq and I can't use the volume control on my monitor with my new Stealth 3D card. The volume is controled by the mother board from the monitor to the sound card. I'd like to make a patch cable to fix this problem. I can't seem to get the answer I want from Compaq.

The user himself finds the solution on http://www.interlog.com/~gscott/t-DB15VGA.html

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12. WARNING

WARNING : THESE PINOUTS ARE OF THOSE CABLES WHICH I USED SUCCESSFULLY, THEN OPENED AND EXAMINED BY ME FOR YOU. BUT PLEASE USE THIS INFO AT YOUR OWN RISK AND DON'T HOLD RESPONSIBLE TO ME IF YOU MESS IT UP. NOBODY IS PERFECT AND THAT INCLUDES ME.

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