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Electronics Initialization
EPRDY signal
This signal is asserted by the print engine to inform the controller that the engine is
ready for communication. When this signal goes true, the controller may poll the
engine status by sending the "Basic Read Status" command.
SYNC signal
When power is turned on, the engine asserts the SYNC signal (raster sync) at fixed
intervals (937.5 µsec for 240 dpi, 750 µsec for 300 dpi, or 562.5 µsec for 400 dpi) in
order to indicate the horizontal scanning start time for printing.
Program load
While the engine is initializing the MPU board (see below), the controller loads the
software from the floppy disk.
MPU initialization
The engine performs a memory check/initialization and a timer initialization.
Wait for controller
After performing the MPU initialization, the engine will wait for the controller board
to finish loading the software and begin its initialization. At this point, the engine
will be in a fault state because the CPRDY signal from the controller will not yet be
asserted. As a result, the RDY signal from the engine will not be asserted.
RESET engine
After the software loads and begins its initialization, it will assert the CPRDY signal,
and then send a RESET command the to engine. This causes it to clear the error
caused by the CPRDY signal being de-asserted (above), and begin mechanical
initialization.
RDY signal assertion
If no errors are found while the mechanical initialization is being performed, the
engine will assert the RDY signal and will be ready to begin printing.
5–58
Principles of Operation
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