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Theory of Operation 2-8
NovaJet 800 Series Service Manual
Main PWA LED Status Indicators
D1 - Normally flashes when the DSP is idle. Steady during print opera-
tions.
D8 - +24V available.
D9 - Normally flashes when the Power PC processor is idle. Stops
flashing when processor is busy (i.e. during paper sensing operations or
printing).
D10 - Normally OFF; Flashes during initialization, then turns off. LED
staying on would indicate a problem when the FPGA is unconfigured.
Ensures the gate array chips have been properly programmed (one on
Main PWA and on each Carriage PWA).
D13 - +5V available.
Microprocessor (CPU)
The microprocessor (a 48MHz PowerPC 860 from Motorola) is the
central processor unit which supervises system functions, executes the
printer firmware, manipulates data, and controls input/output data busses.
It has four built-in serial ports, a two channel DMA (Direct Memory
Access) controller, a timer module, clock generator, and an on-board chip
select generator. The serial ports are not used and are disabled in all
shipping firmware. One DMA channel is used to receive data through
the parallel port via the gate array. One timer generates a servo interrupt
every millisecond; another is used to coordinate firmware multi-tasking.
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.