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Theory of Operation 2-7
NovaJet 500/630/700 Series Service Manual
THEORY OF
OPERATION
Microprocessor
The microprocessor (an IBM PowerPC) is the central processor unit
which supervises system functions, executes the printer firmware,
manipulates data, and controls input/output data busses. It has two
built-in serial ports, a two channel DMA (Direct Memory Access)
controller, a timer module, clock generator, and an on-board chip
select generator. One serial port connects to the Mini-DIN connector
which can be used to communicate with the host computer; the other
serial port interfaces to the Control Panel. One DMA channel sup-
plies data to the gate array for jet firing; the other DMA channel is
used to receive data through the parallel port via the gate array, or
the serial port when using a high speed serial mode. One timer
generates a servo interrupt every millisecond; the other is used for
timing the Stepper Motor.
A divide-by-two circuit generates the 33MHz system clock from a
66MHz crystal reference (X1).
The chip select generator is programmed to generate chip selects at
the appropriate addresses, with the appropriate data size (byte, word)
and with the appropriate number of wait states.
Gate Array
PARALLEL
PORT
GATE
ARRAY
SERVO
CONTROLLER
TO
CARRIAGE
PWA
STATIC
RAM
Figure 2-6. Gate Array.