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C-5
Appendix C
Host Computer Interface
Data 0 [1] to Data 7 [8] (Pins 2 to 9)
These eight signals form the data byte sent from the host computer to the printer. Data 7 [8] is the
most significant bit.
Acknowledge* [nAck] (Pin 10)
This negative-going pulse acknowledges the previous character received by the printer.
Acknowledge* pulses are sent only when Busy is low.
Busy [Busy] (Pin 11)
This signal is high when the printer is busy and low when it is able to accept more data. Every
high-to-low transition is followed by an Acknowledge* pulse.
Paper Empty [PError] (Pin 12)
This signal goes high when the printer runs out of paper.
On-Line [Select] (Pin 13)
This signal is high when the printer is on-line and low when the printer is off-line. It goes low when
the upper unit is raised, or when the ON LINE key is pressed to set the printer off-line.
Note
The Paper Empty and On-Line signals are not used unless enabled by the FRPO command (O2
parameter).
Auto-Feed [nAutoFd] (Pin 14)
This signal is used in the Epson version of the Centronics interface to receive a carriage return. In
high-speed mode, it is used as an interrupt.