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Appendix A System Interface Description
A-8
2.2 Transmission Protocol Description
After Power-ON the PE (Paper Empty) signal is set to low level and the SELECT
and ¯¯¯¯¯FAULT signals are set to high level.
The printer is now ON-LINE and ready to receive data.
Timing
The host sets a print/control character to the 8 data lines.
After a time delay of a minimum of 0.5 µs, the host sends a ¯¯¯¯¯¯STROBE pulse of a
minimum of 0.5 µs. When the data byte is accepted into the interface buffer the
printer transmits a BUSY signal and an ¯¯¯¯ACKN pulse.
The ¯¯¯¯ACKN pulse informs the host that the data has been received and that the
printer is ready to receive new data.
If the interface buffer is full except for the last character the BUSY is not reset in
order to stop the data transfer from the host. The BUSY signal is only reset if
space is available in the interface buffer for a minimum of 512 characters.
While the printer is offline, or a serial interface is active BUSY remains high and
no ¯¯¯¯ACKN is sent until the printer enters online state or the serial interface is
deselected.