Pinouts Assignments
Description
Push-fit multiway connector used mainly on computer equipment.
So called due to the 'D' shape of the shell.
Available in 9, 15, 19, 23, 25, 37 and 50-way versions.
15-way high density types have 15 pins in a 9-way sized shell.
Cable mounted connectors are normally made by fitting a cover to a chassis-mount connector.
PCB mounting and IDC connectors are also available.

Typical Applications

Computers & Peripherals - Serial, Parallel, Monitor & Games connections

Other applications where a low voltage multi-way connector is required.

Pin Assignments
RS232C Serial Ports (9-pin & 25-pin):
There are 2 types of RS232C ports,
DTE (Data Terminal Equipment) and DCE (Data Communications Equipment).
The difference between them is the connections in the plug / socket - the TXD and RXD lines,
and the handshake lines, are reversed.
Serial ports are normally of the DTE type and modems etc. should have DCE ports.
However serial printers often have DTE types.
To connect a DTE port to a DCE port a straight through lead is needed
, i.e. pin 1 to 1, 2 to 2 etc.
To connect 2 DTE or 2 DCE ports, a cross-connected lead is required
, called a null modem lead.
If in doubt just try both and see which works.
Handshaking connections can also cause additional problems.
The table below shows the connections for 9 way and 25 way DTE and DCE ports:
DTE DCE
Function 9-pin 25-pin 9-pin 25-pin
TXD 3 2 2 3
RXD 2 3 3 2
RTS 7 4 8 5
CTS 8 5 7 4
DSR 6 6 4 20
DTR 4 20 6 6
DCD 1 8    
RI 9 22    
GROUND 5 7 5 7
SHIELD GROUND CAN * 1 CAN * 1

* - This should be connected to the screen of the connecting cable.

For a straight lead, connect pin 1-1, 2-2 etc.

For a null modem lead, connect as follows:

9-pin to 9-pin: 2 to 3, 3 to 2, 4 to 6+1, 5 to 5, 6+1 to 4, 7 to 8, 8 to 7
25-pin to 25-pin: 2 to 3, 3 to 2, 20 to 6+8, 7 to 7, 6+8 to 20, 4 to 5, 5 to 4.
9-pin to 25-pin: 2 to 2, 3 to 3, 4 to 6+8, 5 to 7, 6+1 to 20, 7 to 5, 8 to 4.

Parallel Port (Bi-directional, 25-pin):
Pin Direction (From Computer) Function
1 Out Strobe
2 Bi-directional Data 0
3 Bi-directional Data 1
4 Bi-directional Data 2
5 Bi-directional Data 3
6 Bi-directional Data 4
7 Bi-directional Data 5
8 Bi-directional Data 6
9 Bi-directional Data 7
10 In Acknowledge
11 In Busy
12 In Error
13 In Select
14 Out Autofeed
15 In Fault
16 Out Initialise
17 Out SelectIn
18-25 N/A Ground
Older computers with uni-directional parallel ports use the same connections,
however the data lines 0-7 are output-only.
Joystick / MIDI Port (15-pin):
Pin Function
1 +5V DC
2 Button 1
3 Joystick 1 - X
4 Ground
5 Ground
6 Joystick 1 - Y
7 Button 2
8 +5V DC
9 +5V DC
10 Button 4
11 Joystick 2 - X
12 MIDI Transmit / Ground *
13 Joystick 2 - Y
14 Button 3
15 MIDI Receive / +5V DC *
Note that the port has input for 2 joysticks, a splitter lead is required to connect both.
* - Ports without MIDI have pins connected to 5V / Ground.
Pin VGA / SVGA Video (15-pin  High Density & 9-pin):
Function
9-pin VGA 15-pin HD VGA 15-pin VESA DCC (PnP)
1 Red Red Red
2 Green / Mono Green / Mono Green / Mono
3 Blue Blue Blue
4 Horizontal Sync ID Bit 2 Reserved
5 Vertical Sync Ground Ground
6 Red Ground Red Ground Red Ground
7 Green / Mono Ground Green / Mono Ground Green / Mono Ground
8 Blue Ground Blue Ground Blue Ground
9 Sync Ground No Pin +5V DC
10 - Sync Ground Sync Ground
11 - ID Bit 0 ID Bit 0
12 - ID Bit 1 DCC Serial Data
13 - Horizontal or Comp. Sync Horizontal or Comp. Sync
14 - Vertical Sync Vertical Sync
15 - ID Bit 3 DCC Serial Clock
Note that the ID bits are inputs to the computer and are optional.
VESA DCC supports plug-and-play operation and is used by all modern monitors and video adapters.
The serial clock and data lines are bi-directional. All other signal lines are outputs.
Serial Mouse (9-pin):
Pin Function
1 Data
5 Ground (0V)
8 +5V DC
9 Clock
All other pins unused
AUI Thick Ethernet Port (15-pin):
Pin Function
1 Control In Shield
2 Control In A
3 Data Out A
4 Data In Shield
5 Data In A
6 DC Power Common
9 Control In B
10 Data Out B
11 Data Out Shield
12 Data In B
13 DC Power +
14 Power Shield
All other pins unused
IBM Token Ring Network Adapter (9-pin):
Pin Function
1 Ring In
2 Ground
3 +5V DC
4 Ground
5 Ring Out
6 Ring In
7 Ground
8 Ground
9 Ring Out
All other pins unused
Connector Assembly Instructions
Chassis:
Chassis plugs and sockets normally have solder bucket terminations.
Soldering can be difficult to the close spacing of the pins - heatshrink sleeving will help here.
To make a cable-mounted connector a cover can be fitted to the connector.
Note that a 9-way cover will be needed for a 15-way HD connector.
PCB Mounting:
Solder pin connections, normally the connector will have extra pins or lugs for support.
Available in straight or right-angle versions, the latter being more common.
IDC Connection:
Used with ribbon cable to greatly simplify assembly.
Insert cable into connector and squeeze shut with a vice,
this will pierce the insulation and make the connections.
Another advantage is that more than 2 connectors can be fitted to a cable.
Covers are not needed on IDC connectors.