Serial and Parallel Port Pin-Out

Here are the pin assignments for standard RS232 serial and Centronic type parallel port connections. These may be useful in building or testing external A/D interfaces.

Rs-232 Serial (Com) Pc Port Connector Db-9

DB-9 PIN (Male) FUNCTION ABBREVIATION
1 --------------------------- Data Carrier Detect CD or DCD
2 ------------------------------ Receive Data RD or RX
3 ---------------------------- Transmitted Data TX or TD
4 ---------------------------- Data Terminal Ready DTR
5 ------------------------------ Signal Ground GND
6 ------------------------------ Data Set Ready DSR
7 ------------------------------ Request To Send RTS
8 ------------------------------ Clear To Send CTS
9 ------------------------------ Ring Indicator RI
Transmitted and receive data are referenced from the data device and
not the modem.

Rs-232 Serial (Com) Pc Port Connector Db-25

DB-25 PIN (Male) FUNCTION ABBREVIATION
1 ---------------------------- Chassis/Frame Ground GND
2 ------------------------------ Transmitted Data TX or TD
3 -------------------------------- Receive Data RX or RD
4 ------------------------------ Request To Send RTS
5 ------------------------------- Clear To Send CTS
6 ------------------------------- Data Set Ready DSR
7 ------------------------------- Signal Ground GND
8 ---------------------------- Data Carrier Detect DCD or CD
9 ------------------------- Transmit + (Current loop) TD+
11 ------------------------ Transmit - (Current Loop) TD-
18 ------------------------- Receive + (Current Loop) RD+
20 --------------------------- Data Terminal Ready DTR
22 ----------------------------- Ring Indicator RI
25 ------------------------- Receive - (Current Loop) RD-
NOTE!! Current loop technology was supported in the PC and XT interfaces.
Current loop was discontinued when the AT interface was introduced.
Transmitted and receive data are referenced from the data
device and not the modem.

Parallel Printer Connector Db-25

DB-25 PIN (Female) SIGNAL
DB-25 MALE CONN DB-25 FEMALE CONN

1 ------------------------------- > STROBE *
2 ------------------------------- > DATA 0
3 ------------------------------- > DATA 1
4 ------------------------------- > DATA 2
5 ------------------------------- > DATA 3
6 ------------------------------- > DATA 4
7 ------------------------------- > DATA 5
8 ------------------------------- > DATA 6
9 ------------------------------- > DATA 7
10< ------------------------------ ACK *
11< ------------------------------ BUSY
12< ------------------------------ PAPER END
13 ------------------------------ SLCT (select)
14 ------------------------------ >AUTOFEED *
15< ------------------------------ ERROR *
16 --------------------------->INITIALIZE PRINTER *
17 ------------------------------- SLCTIN (select in)
18 thru 25 ----------------------- GND
Note!! * denotes an active low signal.