IBM PC DB-25 Parallel port description & pinout (centronix)

Controlling IBM parallel port lines

Msdos interlink cable or Lap-link cable using IBM parallel port

Msdos interlink cable using IBM serial port NULL-MODEM

IBM PC DB-25 Serial port description & pinout (uart)

Scart (TV) connector description

IBM Vga standard Mini D-Sub 15 pin connector pinout

IBM PC-AT mini DB-9 serial port connector & pinout (uart)

IBM PC DB-15 joystick connector & pinout (game port)

IBM PC AT 5-pin DIN Keyboard connector pinout
 

 

pin	description	pin	description
1	strobe	14	auto feed
2	db 0	15	error
3	db 1	16	initialize printer
4	db 2	17	select input
5	db 3	18	ground
6	db 4	19	ground
7	db 5	20	ground
8	db 6	21	ground
9	db 7	22	ground
10	acknowledge	23	ground
11	busy	24	ground
12	paper out	25	ground
13	select	.	.

Notes: this connector is female
Pin 17, select input: allows computer to set on/off line some printers. (on-line if LOW)
Pin 13, select: is HI if printer is on-line, else is LOW
Pin 14, Auto feed: if LOW is enabled, if you switch off your computer while you are printing dos text Pin 14 goes LOW, so there is a double line feed.
 

View now a msdos Qbasic example program, save it, and try!

(&H is Hexadecimal)

Hardware Required	"Software" Port Address
Monochromatic Display Adaptor (MDA) parallel port	&H3BC
Primary parallel port	&H378
Secondary parallel port	&H278
Third parallel port (same address of MDA parallel port)	&H3BC

Parallel port is controlled by 3 registers: CONTROL INPUT and CONTROL OUTPUT registers are latched; OUTPUT DATA is impulsive.

HI is +5 Volt from ground (pin 25). LOW is 0 Volt from ground (pin 25)

1) OUTPUT DATA software address: Port address + 0
this register allows to write (ad often to read) the data lines (db-0 up to db-7) but this lines are impulsive.

2) CONTROL INPUT software address: Port address + 1

Bit	Description
0	not used
1	not used
2	not used
3	error: it's 1 if error line (pin 15) is HI
4	select: it's 1 if select line (pin 13) is HI
5	paper: it's 1 if paper line (pin 12) is HI
6	ack: it's 1 if acknowledge line (pin 10) is HI
7	busy: it's 0 if busy line (pin 11) is HI (inverting)

To set pin 10-15 to LOW connect it directly to ground (pin 25); To set pin 10-15 to HI disconnect it from any other one.

3) CONTROL OUTPUT software address: Port address + 2

Bit	Description
0	strobe: inverting, if it's 1 then strobe line (pin 1) is LOW
1	auto feed: inverting, if it's 1 then auto feed line (pin 14) is LOW
2	init: if it's 1 then initialize printer line (pin 16) is HI
3	select input: inverting, if it's 1 then select input line (pin 17) is LOW
4	enable int: it is a software control, enables interrupt request
5	not used
6	not used
7	not used

One End	Other End	Description
shield	shield	-
2	15	db-0 to error
3	13	db-1 to select
4	12	db-2 to paper out
5	10	db-3 to acknowledge
6	11	db-4 to busy
10	5	acknowledge to db-3
11	6	busy to db-4
12	4	paper out to db-2
13	3	select to db-1
15	2	error to db-0
25	25	ground to ground

Notes: I've made also a cable with one wire less: connect shield to pin 25 (ground) to each side. (It works well)
Data lines are connected to error line, to enable a asynchronous, fast, interrupt driven transmitting data.

 

pin	description	pin	description
.	shield	20	input video
19	output video	18	ground
17	ground	16	blanking
15	input red	14	n.c.
13	ground	12	n.c.
11	input green	10	n.c.
9	ground	8	monitor (AV)=+12Volt
7	input blue	6	input audio L
5	ground	4	ground
3	output audio L	2	input audio R
1	output audio R	-	-

Notes:this connector is female
It's possible to make a simple connector from VGA to SCART but needs a bit of electronics for synchronism signals: I've made this circuit but, it doesn't work: the matter should be my-tv-scart-in-connector, does it get RBG signals? Should not :(
It's also possible to make a connector from SCART to VGA (example using a VGA Monitor for video-recorder output, but I've never succeed in: like tv, my-video-recorder-scart-out-connector does not support RGB components... :(

 

DB-25 Pin	EIA	Description	DB-25 Pin	EIA	Description
14	SBA	secondary transmitted data	1	FG	protective ground
15	TC	transmitter clock	2	TXD	transmit data
16	SBB	secondary received data	3	RXD	receive data
17	RC	receiver clock	4	RTS	request to send
18	-	unassigned	5	CTS	clear to send
19	SCA	secondary request to send	6	DSR	data set ready
20	DTR	data terminal ready	7	GND	signal ground
21	SQ	signal quality	8	DCD	carrier detect
22	RI	ring indicator	9	-	reserved
23	?	data signal rate select	10	-	reserved
24	ETC	external transmitter clock	11	-	unassigned
25	-	unassigned	12	SCF	secondary received line signal detector
-	-	-	13	SCB	secondary clear to send

Notes: this connector is male

For a SAFE computer connection, use a cable with this pin connections. I have made a connector 13 meters long, and it works well. This description is DB-25 or DB-9 UART connector.

DB-25 One End	DB-25 Other End	DB-9 One End	DB-9 Other End	Description
1	1	-	-	protective ground --- to --- protective ground
2	3	3	2	transmit data --- to --- receive data
3	2	2	3	receive data --- to --- transmit data
5, 6, 8  Connect all in one	20	8,6,1 Connect all in one	4	clear to send & data set ready & data terminal ready (of SAME SIDE): connect all in one, then with this wire --- to --- data terminal ready
7	7	5	5	signal ground --- to --- signal ground
20	8, 6, 5  Connect all in one	4	8,6,1 Connect all in one	data terminal ready --- to --- wire coming from clear to send & data set ready & data terminal ready (of SAME SIDE), connected all in one
shield	shield	shield	shield	.

Notes: Pin 1, is OFTEN NOT connected in some cables: CONNECT IT! If you don't, it may cause (for long wires) a UART destruction.

 

DB-9 Pin	EIA	Description	DB-25 equivalent pin
1	DCD	data carrier detect	8
2	RXD	received data	3
3	TXD	transmit data	2
4	DTR	data terminal ready	20
5	GND	signal ground	7
6	DSR	data set ready	6
7	RTS	request to send	4
8	CTS	clear to send	5
9	RI	ring indicator	22

Notes: This connector is male
protective ground does not exists.

 

Pin	Joy Port Description
1	common x1, y1 +5 volt
2	switch 1 +
3	x1
4	switch 1 ground
5	switch 2 ground
6	y1
7	switch 2 +
8	not connected
9	common x2, y2 +5 volt
10	switch 4 +
11	x2
12	common switch 3&4 ground
13	y2
14	switch 3
15	not connected

Notes: this connector is female

To read Joystick status you can:
1) call BIOS routines
2) directly read joy status
 

1) Calling Bios Routines
Bios interrupt 015h, subfuction 084h returns joy status. How to call:

To read switches status	To read trimmers status
AH=084h, DX=000h, call INT 015h  returns:  On any error carry flag is set.  If no error occurs, AL contains switches status (from bit 4 up to bit 7)	AH=084h, DX=001h, call INT 015h  returns:  On any error carry flag is set.  If no error occurs, AX contains first trimmer status, BX second, CX third, DX fourth

2) Reading directly to Joy port
To read trimmers status you have to write any data to this port to start timing for the resistive values. Then you have to wait up to trimmer's bit goes hi. Measure for each trimmer this time, so use this formula to compute resistance of trimmer:

resistance=(time - 24.2)/0.011
(I don't know unit measure)
 

Software port number is 0201h, bits description follow

bit	description
0	joystick 1, x cord (0 = timing active, set it to 0 to start timing)
1	joystick 1, y cord (0 = timing active, set it to 0 to start timing)
2	joystick 2, x cord (0 = timing active, set it to 0 to start timing)
3	joystick 2, y cord (0 = timing active, set it to 0 to start timing)
4	joystick 1, button 1 (0=pressed)
5	joystick 1, button 2 (0=pressed)
6	joystick 2, button 1 (0=pressed)
7	joystick 2, button 2 (0=pressed)

 

Mini D-SUB 15 Pin	Signal
1	Red Video
2	Green Video
3	Blue Video
13	Horizontal Sync
14	Vertical Sync
4,5,6,7,8,10,11	Ground
12	SDA (DDC)
15	SLC (DDC)
9	?

Notes: this connector is female

 

Pin	Description
1	Keyboard Clock
2	Keyboard Data
3	n.c.
4	Ground
5	Power Supply (+5 Volt)

 

Ballardini Tsuyoshi (TBN) ;-)
Stefano Converso
and... LACAB