Appendix A System Interface Description
A-9
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.
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