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QUICK GUIDE TO COMPUTER CABLES
by Bill Becwar
LEGAL STUFF - This guide is as complete and accurate as I can make
it, however, I can't be responsible for errors, omissions, typing
mistakes, bad downloads, or your dog biting you. I know that
somebody, somewhere is going to cross a wire. Best advice if you
want to build one of these cables: Complete the wiring all in one
work session. Then check the connections, preferably with an
ohmmeter. Go away for a while and do something else, then return
and CHECK the connections again. If you have any comments or find
any errors, leave E-Mail to William Becwar on EXEC-PC, the largest
and finest BBS in the country, (414) 789-4210, or on CompuServe
72060,251. Good Luck!
POWER SUPPLY CONNECTORS -
Typical Power Supply has 6 Connectors: 2 ea. - 6 pin for
Motherboard Power and 4 ea. - 4 pin for Disk Drive Power.
Motherboard Power Connectors
P8 P9
Pin Signal Pin Signal
----------------------------- ---------------------------
1 - Power Good 1 - GND
2 - +5v (or N.C.) 2 - GND
3 - +12v 3 - -5v
4 - -12v 4 - +5v
5 - GND 5 - +5v
6 - GND 6 - +5v
Disk Drive Power Connectors (4 - 4 pin)
Pin Signal
-----------------------------
1 - +12v
2 - GND
3 - GND
4 - +5v
MOTHERBOARD CONNECTORS -
Motherboards have various combinations of connectors depending
on design type and built-in facilities. These will be found in a
typical clone.
Backup Battery Connector (AT only)
Pin Signal
-----------------------------
1 - Batt+
2 - [KEY]
3 - GND
4 - GND
LED Power and Key Lock (AT only)
Pin Signal
-----------------------------
1 - LED power
2 - GND
3 - GND
4 - Key Switch
5 - GND
Speaker Connector
Pin Signal
-----------------------------
1 - -Speaker
2 - [KEY]
3 - GND
4 - +Speaker +5v
Turbo Indicator Connector
Used only on Turbo switchable machines. Safest Connector on
the machines that have it; can't be connected backwards!
Pin Signal
-----------------------------
1 - +5v
2 - *HIGH SPEED
3 - +5v
MOTHERBOARD I/O CARD EXPANSION SLOTS
Not exactly for cabling, but a good reference anyway.
8-bit slots (PC/XT/AT)
COMPONENT SIDE NON-COMPONENT SIDE
Pin Signal Pin Signal
--------------- ---------------
A1 -I/O CH CLK B1 GND
A2 SD7 B2 RESET DRV
A3 SD6 B3 +5v
A4 SD5 B4 IRQ 9
A5 SD4 B5 -5v
A6 SD3 B6 DRQ 2
A7 SD2 B7 -12v
A8 SD1 B8 Reserved / OWS
A9 SD0 B9 +12v
A10 -I/O CH RDY B10 GND
A11 AEN B11 -SMEMW
A12 SA19 B12 -SMEMR
A13 SA18 B13 -IOW
A14 SA17 B14 -IOR
A15 SA16 B15 -DACK3
A16 SA15 B16 DRQ3
A17 SA14 B17 -DACK1
A18 SA13 B18 DRQ1
A19 SA12 B19 -REFRESH
A20 SA11 B20 CLK
A21 SA10 B21 IRQ7
A22 SA9 B22 IRQ6
A23 SA8 B23 IRQ5
A24 SA7 B24 IRQ4
A25 SA6 B25 IRQ3
A26 SA5 B26 -DACK2
A27 SA4 B27 T/C
A28 SA3 B28 BALE
A29 SA2 B29 +5v
A30 SA1 B30 OSC
A31 SA0 B31 GND
Motherbaord Expansion slots continued...
16-bit Slots (AT only)
COMPONENT SIDE NON-COMPONENT SIDE
Pin Signal Pin Signal
--------------- ---------------
C1 SBHE D1 -MEM CS16
C2 LA23 D2 -I/O CS16
C3 LA22 D3 IRQ10
C4 LA21 D4 IRQ11
C5 LA20 D5 IRQ12
C6 LA19 D6 IRQ13
C7 LA18 D7 IRQ14
C8 LA17 D8 -DACK0
C9 -MEMR D9 DRQ0
C10 -MEMW D10 -DACK5
C11 SD08 D11 DRQ5
C12 SD09 D12 -DACK6
C13 SD10 D13 DRQ6
C14 SD11 D14 -DACK7
C15 SD12 D15 DRQ7
C16 SD13 D16 +5v
C17 SD14 D17 -MASTER
C18 SD15 D18 GND
Keyboard Connector
Pin Signal
-----------------------------
1 - KBD CLK OUT
2 - KBD SERIAL OUT
3 - KBD RESET IN
4 - KBD GND
5 - KBD +5v
FLOPPY DISK CABLES -
Floppy / Hard Drive Power Connectors
Pin Signal
-----------------------------
1 - +12v
2 - GND
3 - GND
4 - +5v
Floppy Disk Drive Interface Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - GND 2 - N/C
3 - GND 4 - N/C
5 - GND 6 - N/C
7 - GND 8 - Index
9 - GND 10 - Motor Enable A
11 - GND 12 - Drive Select B
13 - GND 14 - Drive Select A
15 - GND 16 - Motor Enable B
17 - GND 18 - Stepper Direction
19 - GND 20 - Step Pulse
21 - GND 22 - Write Data
23 - GND 24 - Write Enable
25 - GND 26 - Track 0
27 - GND 28 - Write Protect
29 - GND 30 - Read Data
31 - GND 32 - Select Head 1
33 - GND 34 - (Spare)
HARD DISK CABLES -
ST-506 Hard Disk Drive Control/Data Cables
Floppy / Hard Drive Power Connectors
Pin Signal
-----------------------------
1 - +12v
2 - GND
3 - GND
4 - +5v
ST-506 Control Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - Head Select 8 2 - GND
3 - Head Select 4 4 - GND
5 - Write Gate 6 - GND
7 - Seek Complete 8 - GND
9 - Track 0 10 - GND
11 - Write Default 12 - GND
13 - Head Select 1 14 - GND
15 - Reserved 16 - GND
17 - Head Select 2 18 - GND
19 - Index 20 - GND
21 - Ready 22 - GND
23 - Step 24 - GND
25 - Drive Select 1 26 - GND
27 - Drive Select 2 28 - GND
29 - Drive Select 3 30 - GND
31 - Drive Select 4 32 - GND
33 - Direction In 34 - GND
ST-506 Data Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - Drive Selected 2 - GND
3 - Reserved 4 - GND
5 - Reserved 6 - GND
7 - Reserved 8 - GND
9 - Reserved 10 - GND
11 - GND 12 - GND
13 - MFM Write Data+ 14 - MFM Write Data-
15 - GND 16 - GND
17 - MFM Read Data+ 18 - MFM Read Data-
19 - GND 20 - GND
ESDI Hard Disk Drive Control/Data Cables
ESDI Control Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - Head Select 3 2 - GND
3 - Head Select 2 4 - GND
5 - Write Gate 6 - GND
7 - Config/Status Data 8 - GND
9 - Transfer Ack. 10 - GND
11 - Attention 12 - GND
13 - Head Select 0 14 - GND
15 - Sec/Addr Mark Find 16 - GND
17 - Head Select 1 18 - GND
19 - Index 20 - GND
21 - Ready 22 - GND
23 - Transfer Request 24 - GND
25 - Drive Select 1 26 - GND
27 - Drive Select 2 28 - GND
29 - Drive Select 3 30 - GND
31 - Read Gate 32 - GND
33 - Command Data 34 - GND
ESDI Data Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - Drive Selected 2 - Sec/Addr Mark Found
3 - Seek Completed 4 - Address Mark Enable
5 - Reserved/Step Mode 6 - GND
7 - Write Clock+ 8 - Write Clock-
9 - Cartridge Changed 10 - Read Ref. Clock+
11 - Read Ref. Clock- 12 - GND
13 - NRZ Write Data+ 14 - NRZ Write Data-
15 - GND 16 - GND
17 - NRZ Read Data+ 18 - NRZ Read Data-
19 - GND 20 - Index
SCSI Hard Disk Drive Interface Cable
Pin Signal Pin Signal
-------------------------------------------------------------
1 - GND 2 - Data Line 0
3 - GND 4 - Data Line 1
5 - GND 6 - Data Line 2
7 - GND 8 - Data Line 3
9 - GND 10 - Data Line 4
11 - GND 12 - Data Line 5
13 - GND 14 - Data Line 6
15 - GND 16 - Data Line 7
17 - GND 18 - Data Parity Line
19 - GND 20 - GND
21 - GND 22 - GND
23 - GND 24 - GND
25 - N/C 26 - Terminator Power
27 - GND 28 - GND
29 - GND 30 - GND
31 - GND 32 - Attention
33 - GND 34 - GND
35 - GND 36 - Busy
37 - GND 38 - Acknowledge
39 - GND 40 - Reset
41 - GND 42 - Message
43 - GND 44 - Select
45 - GND 46 - C/D
47 - GND 48 - Request
49 - GND 50 - I/O
DISPLAY ADAPTOR CONNECTORS -
Monochrome (MDA), Hercules, Color (CGA) Adaptors
Connector type - DB-9
Pin Signal Pin Signal
-------------------------------------------------------------------
1 GND 6 Intensity
2 GND 7 Video *
3 N/C or RED 8 Horizontal Drive
4 N/C or GREEN 9 Vertical Drive
5 N/C or BLUE
* NTSC Video on some clone boards
EGA Adaptor
Connector Type - DB-9
Pin Signal Pin Signal
-------------------------------------------------------------------
1 GND 6 Secondary Green / Intensity
2 Secondary Red 7 Secondary Blue / Mono Video
3 Primary Red 8 Horizontal Drive
4 Primary Green 9 Vertical Drive
5 Primary Blue
VGA Adaptor
Connector Type - DB-15
Pin Signal Pin Signal
-------------------------------------------------------------------
1 Red Video 9 [KEY]
2 Green Video 10 Sync GND
3 Blue Video 11 Monitor ID - Bit 1
4 - Monitor ID - Bit 2 12 Monitor ID - Bit 0
5 - GND 13 Horizontal Sync
6 - Red GND 14 Vertical Sync
7 - Green GND 15 N/C (Reserved)
8 - Blue GND
PARALLEL PRINTER PORT
I/O Mapping
--------------------------
LPT1: $378-37A
LPT2: $278-27A
DB-25 Connector (Computer End)
Pin Signal Pin Signal
-------------------------------------------------------------------
1 *STROBE 14 *Auto Feed
2 Data Bit 0 15 *Error
3 Data Bit 1 16 *Initialize Printer
4 Data Bit 2 17 *Select Input
5 Data Bit 3 18 GND
6 Data Bit 4 19 GND
7 Data Bit 5 20 GND
8 Data Bit 6 21 GND
9 Data Bit 7 22 GND
10 *Acknowledge 23 GND
11 Busy 24 GND
12 Paper Out 25 GND
13 Select
Centronics 36 pin Connector (Printer End)
Pin Signal Pin Signal
-------------------------------------------------------------------
1 *STROBE 19 GND
2 Data Bit 0 20 GND
3 Data Bit 1 21 GND
4 Data Bit 2 22 GND
5 Data Bit 3 23 GND
6 Data Bit 4 24 GND
7 Data Bit 5 25 GND
8 Data Bit 6 26 GND
9 Data Bit 7 27 GND
10 *Acknowledge 28 GND
11 Busy 29 GND
12 Paper Out 30 GND
13 Select 31 *Prime
14 *Auto Feed XT 32 *Error
15 {OSCXT} 33 Signal GND
16 Signal GND 34 N/C
17 Frame GND 35 N/C
18 +5v 36 N/C
SERIAL PORTS
NOTE: The IBM PC uses a DTE (Data Terminal Equipment) Connection
standard. Most Modems are DCE (Data Communication Equipment).
I/O Map
-----------------------------
COM1: $3F8-3FF
COM2: $2F8-2FF
COM3: $3E8-3EF
COM4: $2E8-2EF
DB-9 Connector
Pin Signal Pin Signal
-------------------------------------------------------------------
1 CD Carrier Detect 6 DSR Data Set Ready
2 RXD Receive Data 7 RTS Request to Send
3 TXD Transmit Data 8 CTS Clear to Send
4 DTR Data Term. Ready 9 RI Ring Indicator
5 GND Signal GND
DB-25 Connector
Pin Signal Pin Signal
-------------------------------------------------------------------
1 GND Ground / Shield 14 {2nd TXD}
2 TXD Transmit Data 15 Transmit Clock
3 RXD Received Data 16 {2nd Rec. Clock}
4 RTS Request to Send 17 {Receive Clock}
5 CTS Clear to Send 18 {Unassigned}
6 DSR Data Set Ready 19 {2nd RTS}
7 GND Ground 20 DTR Data Term Ready
8 DCD Carrier Detect 21 {Sig. Quality}
9 {Reserved} 22 RI Ring Indicator
10 {Reserved} 23 {Data Rate Sel.}
11 {Unassigned} 24 {Transmit Clock}
12 {2nd CD} 25 {Unassigned}
13 {2nd CTS}
NULL MODEM CONNECTION-
RS-232 Definition Computer/Terminal Modem
Signal DTE DCE
9-pin 25-pin 25-pin
-------------------------------------------------------------------
GND Signal GND 5 1 1
TXD Transmit Data 3 2 3
RXD Receive Data 2 3 2
RTS Req. to Send 7 4 5
CTS Clear to Send 8 5 4
DSR Data Set Ready 6 6 20
GND Chassis GND - 7 7
CD Carrier Detect 1 8 8
DTR Data Term. Ready 4 20 6
DTE DCE
1 ??????????????????????? 1
2 ???????????? ?????? 2
?????????????
3 ?????? ???????????? 3
4 ???????????? ?????? 4
?????????????
5 ?????? ???????????? 5
6 ???????????? ?????? 6
? ?
7 ??????????????????????? 7
?????????????
8 ??????????????????????? 8
? ?
20 ?????? ???????????? 20
GAME CONNECTOR
DB-15 Connector
Pin Signal Pin Signal
-------------------------------------------------------------------
1 +5v 9 +5v
2 Button 1-1 10 Button 2-1
3 X1 11 X2
4 GND 12 GND
5 GND 13 Y2
6 Y1 14 Button 2-2
7 Button 1-2 15 N/C
8 N/C
Buttons - Connect from GND to Button inputs
X and Y pots connect from +5v to X-Y inputs.
JOYSTICK CONNECTOR
DB-9 Connector
Pin Signal Pin Signal
-------------------------------------------------------------------
1 JOY0 6 Fire Button
2 JOY1 7 +5v
3 JOY2 8 GND
4 JOY3 9 POT X
5 POT Y