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Parallel cables pinout and port info

Parallel cables

Standard parallel cables are easy to obtain, but the link cable and test connectors which are shown here can often be better soldered by yourself.

Parallel connector pinout

The parallel port socket on your computer uses 25 pins. On most peripherals like printers, the 36 pins Centronics version is used. Both connector pinouts are shown here. The centronics socket is named after the company that introduced the first dot matrix printer in 1970, but after IBM and Epson took over the dot matrix printer market (later followed by Hewlett Packard in the laser and deskjet printer segment) most people only associate the word centronics with the port interface itself, not with a manufacturer.

Parallel DB25 pinout
Parallel DB25 connector
Centronics pinout
Centronics parallel connector

Parallel printer cable

Most printers are connected to a computer using a cable with a 25 pins DB male connector at one side and a 36 pins centronics connector on the other. The normal way to make such a cable is shown here.

Parallel printer cable
Line DB 25 male
Strobe 1 1
Data bit 0 2 2
Data bit 1 3 3
Data bit 2 4 4
Data bit 3 5 5
Data bit 4 6 6
Data bit 5 7 7
Data bit 6 8 8
Data bit 7 9 9
Acknowledge 10 10
Busy 11 11
Paper out 12 12
Select 13 13
Autofeed 14 14
Error 15 32
Reset 16 31
Select 17 36
Signal ground 18 33
Signal ground 19 19 + 20
Signal ground 20 21 + 22
Signal ground 21 23 + 24
Signal ground 22 25 + 26
Signal ground 23 27
Signal ground 24 28 + 29
Signal ground 25 16 + 30
Shield Cover Cover + 17

Interlink and Windows 95/98/ME DCC parallel cable

The following parellel cable can be used with file transfer and network programs like LapLink and InterLink. The cable uses the parallel port which makes it possible to achieve higher throughput than with a serial connection at the same low costs. The cable is amongst others compatible with the following software.

  • Laplink from Travelling software
  • MS-DOS v 6.xx InterLink
  • Windows 95, 98 and ME direct cable connection
  • Norton Commander
  • Norton Ghost

Because the parallel port on a computer was mainly designed to connect printers with one-way communication, a trick is used to achieve full two way data transfer between both sides. Five error and status message inputs are redefined as data inputs. Instead of reading full bytes, the communication software reads these five bits and combines multiple groups of data back to bytes. The sender and receiver have to use the same protocol to convert bytes to groups of 5 bits and vice versa.

Interlink and Windows 95/98/ME DCC parallel cable
Interlink and Windows 95/98/ME DCC parallel cable

Connector 1 Connector 2 Description
2 15 Data bit 0 Error
3 13 Data bit 1 Select
4 12 Data bit 2 Paper Out
5 10 Data bit 3 Acknowledge
6 11 Data bit 4 Busy
10 5 Acknowledge Data bit 3
11 6 Busy Data bit 4
12 4 Paper Out Data bit 2
13 3 Select Data bit 1
15 2 Error Data bit 0
25 25 Signal ground

Parallel port test plugs

Both Norton Diagnostics and CheckIt have the ability to check the functionality of a parallel port. To do this, both software packages need a special plug on the port. Unfortunately, the pin layout of both connectors is not the same. The scheme of both sockets is given here.

Norton test plug
Norton Diagnostics parallel port test plug
CheckIt test plug
CheckIt parallel port test plug


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