Centronics

36-pin board edge connector interface for external printer connectors and cables

• 8 bit asynchronous data bus
• 1 byte serial / 8 bit parallel point-to-point bus

Pin and signal assignments

15 total signal lines

Data lines

DATA1 - DATA8

pins 1/19, 2/20, 3/21, 4/22, 5/23, 6/24, 7/25, 8/26, and 8/27

Computer to device

Pins 1, 19

STROBE : Data STROBE

Logic low pulse of at least 0.5 microsecond tells device to read byte of data currently present on data lines

Pins 31, 30

INIT : INITialize

Logic low pulse (e.g. of at least 0.5 microseconds) resets device to power-on or default conditions

Device to computer

Pins 10, 28

ACKNLG : ACKNowLedGe

Logic low indicates last byte accepted and device is ready for next

Pins 11, 29

BUSY : Device BUSY

Logic high indicates device can’t receive data due to data entry, full buffer, or error status

Pin 12

Out of Paper

Logic high indicates out of paper

Pin 13

SLCT : SeLeCT

Logic high indicates device is ‘selected’ by user (always high on some devices)

Pin 32

ERROR : Error

Logic low indicates self-test-failure, out of media, device offline, or other hardware error

Grounds

Pin 16

SIG GND : SIGnal GrouND

Pin 17

CHS GND : CHassiS GrouND

Pin 33

SIG GND : SIGnal GrouND

Unused pins (6)

• 14–15
• 18
• 34–36

Pin 14

Epson and IBM define as AUTO FEED XT, with logic low causing printer advancing one line

Pin 36

Epson and IBM define as an logic low SELECT line (-SLCT_IN)

References

• Page 12-2 of http://www.hpmuseum.net/document.php?hwfile=3849