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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
LineDB 25 male
Data bit 022
Data bit 133
Data bit 244
Data bit 355
Data bit 466
Data bit 577
Data bit 688
Data bit 799
Paper out1212
Signal ground1833
Signal ground1919 + 20
Signal ground2021 + 22
Signal ground2123 + 24
Signal ground2225 + 26
Signal ground2327
Signal ground2428 + 29
Signal ground2516 + 30
ShieldCoverCover + 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 1Connector 2Description
215Data bit 0Error
313Data bit 1Select
412Data bit 2Paper Out
510Data bit 3Acknowledge
611Data bit 4Busy
105AcknowledgeData bit 3
116BusyData bit 4
124Paper OutData bit 2
133SelectData bit 1
152ErrorData bit 0
2525Signal 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
Matter will be damaged in direct proportion to its value.
  Aug. 2017
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