3. IBM DB-25 and DB-9 diagrams.

(Each diagram on this page is the view you see when you look into the end of the cable from the outside of the cable.) (Each diagram on this page is the view you see when you look into the end of the cable from the outside of the cable.)

The "o" characters represent holes, the "." characters represent pins.
A DB-25 looks like this... 

Diagram #1
Female:                        Male:
_____________________________  _____________________________
\ o o o o o o o o o o o o o /  \ . . . . . . . . . . . . . /
 \ o o o o o o o o o o o o /    \ . . . . . . . . . . . . /
  -------------------------      -------------------------

And a DB-9 is like this... 

Diagram #2
Female:        Male:
_____________  _____________
\ o o o o o /  \ . . . . . /
 \ o o o o /    \ . . . . /
  ---------      ---------

4. IBM DB-25 and DB-9 numbering scheme. (Pin numbers)

Each pin has a number assigned to it. When connecting null modem, for example, it is important to know these numbers in order to select the correct cables, or when making your own cables.

DB-25 Connector

Chart #1 (Female) 

 
  13              <------- 1
 _____________________________
 \ o o o o o o o o o o o o o /
  \ o o o o o o o o o o o o /
   -------------------------
    25             <----- 14

Chart #2 (Male) 

 
  1 ------->              13
 _____________________________
 \ . . . . . . . . . . . . . /
  \ . . . . . . . . . . . . /
   -------------------------
   14 ----->             25 

DB-9 Connector

Chart #3 (Female) 

 
   5 4 3 2 1
 _____________
 \ o o o o o /
  \ o o o o /
   ---------
    9 8 7 6    

Chart #4 (Male) 

 
   1 2 3 4 5
 _____________
 \ . . . . . /
  \ . . . . /
   ---------
    6 7 8 9   

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5. IBM Serial port Pin Descriptions (Wire name) for each pin number.

For following all connections we may use these chart for transmission of Data via Serial Port. For following all connections we may use these chart for transmission of Data via Serial Port.

Chart#11
Pin assignments
DB-25

2

TD

Transmit Data

3

RD

Receive Data

4

RTS

Request to send

5

CTS

Clear to send

6

DSR

Data Set Ready

7

SG

Signal Ground

8

DCD

Data Carrier Detect

20

DTR

Data Terminal Ready

22

Ring

Ring Indicator

Chart#12
Pin Assignments
DB-9

1

DCD

Data Carrier Detect

2

RD

Receive Data

3

TD

Transmit Data

4

DTR

Data Terminal Ready

5

SG

Signal Ground

6

DSR

Data Set Ready

7

RTS

Request to Send

8

CTS

Clear to Send

9

Ring

Ring Indicator

IMP. NOTE : In DB-25 serial cable following numbered pins are NOT USED. They are 1, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24 and 25. IMP. NOTE : In DB-25 serial cable following numbered pins are NOT USED. They are 1, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 23, 24 and 25.

 

Chart#13
Pin Assignments of Parallel Port (LPT1)
Female DB-25 on PC

<= in
or
=> out

DB25
Pin

Cent
Pin

Name of
Signal

Reg
Bit

Function Notes

=> out

1

1

-Strobe

C0-

Set Low p1ulse >0.5 us to send

=> out

2

2

Data 0

D0

Set to least significant data

=> out

3

3

Data 1

D1

...

=> out

4

4

Data 2

D2

...

=> out

5

5

Data 3

D3

...

=> out

6

6

Data 4

D4

...

=> out

7

7

Data 5

D5

...

=> out

8

8

Data 6

D6

...

=> out

9

9

Data 7

D7

Set to most significant data

<= in

10

10

-Ack

S6+

IRQ; Low Pulse ~ 5 uS, after accept

<= in

11

11

+Busy

S7-

High for Busy/Offline/Error

<= in

12

12

+PaperEnd

S5+

High for out of paper

<= in

13

13

+SelectIn

S4+

High for printer selected

=> out

14

14

-AutoFd

C1-

Set Low to autofeed one line

<= in

15

32

-Error

S3+

Low for Error/Offline/PaperEnd

=> out

16

31

-Init

C2+

Set Low pulse > 50uS to init

=> out

17

36

-Select

C3-

Set Low to select printer

==

18-25

19-30,
33,17,16

Ground

-

Do not connect any of these grounds to a shield

 

Chart#5

DCC Parallel Laplink Cable Pinouts.

Male DB-25

==>>

Male DB-25

1

Both Not used

2

To

15

3

To

13

4

To

12

5

To

10

6

To

11

7

Both Not used

8

Both Not used

9

Both Not used

10

To

5

11

To

6

12

To

4

13

To

3

14

Both Not used

15

To

2

16

Both Not used

17

To

19

18

To

18

19

To

17

20

Both Not used

21

To

21

22

To

22

23

To

23

24

Both Not used

25

To

25

Pinbody*

To

Pinbody

Chart #6

Chart #7

Chart #8

Null-Modem Pinouts
DB-25 to DB-25

2

to

3

3

to

2

4

to

5

5

to

4

6 and 8

To

20

7

To

7

20

To

6 and 8

Null-Modem Pinouts
DB-9 to DB-9

1 and 6

to

4

2

to

3

3

to

2

4

to

1 and 6

5

to

5

7

to

8

8

to

7

Null-Modem Pinouts
DB-25 to DB-9

2

to

2

3

to

3

4

to

8

5

to

7

6 and 8

to

4

7

to

5

20

to

6 and 1

Chart #9

Chart #10

Normal-Modem Pinouts
DB-25 to DB-25

2

to

2

3

to

3

4

to

4

5

to

5

6

to

6

7

to

7

8

to

8

20

to

20

22

to

22

PinBody*

to

Pinbody*

Normal-Modem Pinouts
DB-25 to DB-9

2

to

3

3

to

2

4

to

7

5

to

8

6

to

6

7

to

5

8

to

1

20

to

4

22

to

9

PinBody*

to

Pinbody*

Chart# 14

DB9 Pinouts of
STRAIGHT SERIAL PORT
on 286/386 systems

Cable Wire number
on motherboard

Wire Connected
to male DB9 pin
on cabinet.

1 Red Wire

1

2

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

Chart# 15

DB9 Pinouts of
TWISTED TYPE SERIAL PORT
on modern systems

Cable Wire number
on motherboard

Wire Connected
to male DB9 pin
on cabinet.

1 Red Wire

1

2

6

3

2

4

7

5

3

6

8

7

4

8

9

9

5

Chart# 16

DB25 Pinouts of
STRAIGHT SERIAL PORT
on 286/386 systems

Cable Wire number
on motherboard

Wire Connected
to male DB25 pin
on cabinet.

1 Red Wire

8

2

3

3

2

4