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NovaJet 800 Series Service Manual
A hardware counter in the gate array increments as the Carriage Assem-
bly moves left and decrements as the Carriage Assembly moves right.
The hardware counter is only eight bits wide, so it cannot store a value
large enough to represent an absolute Carriage Assembly position.
Instead, it is read during the servo interrupt and its value compared with
that from the previous interrupt. This difference is used to update the
absolute position value in the software.
Interface Circuits: Serial & Parallel
MICRO-
GATE
PARALLEL
PROCESSOR
ARRAY
CONNECTOR
Figure 2-10. Interface Circuits.
Data from the host computer is received through the Centronics parallel
port. The gate array provides the control signals for DMA transfers from
the parallel port to SDRAM.
The serial port is not used.
Possible solutions for the Macintosh computer user include using the print
server device with an established network or installing a parallel port add-
on card in the computer to interface with the printer.
Theory of Operation
2-15
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