Repair manual

2-26
THEORY OF OPERATION
When the Digital Palette operator momentarily presses the
RESET switch, the Reset Control circuit generates a reset signal
that initializes the Microprocessor Control network and its
associated circuitry. The reset signal from the RC network of the
Reset Control circuit is ac coupled so that the switch can bepressed
for an extended period of time (in the order of a few
seconds). In most cases, it is released quickly resulting in a very
short reset signal that causes the microprocessor and its associated
circuitry to be initialized.
If the RESET switch is held in (pressed) for an extended period of
time, the microprocessor still initializes the Digital Palette but
it also reads the state of the pressed RESET switch. Once the
microprocessor determines that the RESET switch is in its pressed
state, the microprocessor flags the resident test image program for
the applicable EPROM and then initiates an exposure sequence of
the resident test image.
3) Host Computer Reset
The Microprocessor Control Network and its associated circuitry
can also be initialized by the host computer prior to or during an
exposure sequence of the computed-generated image. In fact, a
RESET command is typically the first command issued by a host
computer application.
If a RESET command is sent to the Digital Palette by the host
computer, it does not affect the exposure state or any images that
are completely buffered for an exposure. A prior image that was
completely transmitted will be properly exposed. Any partially
transmitted image will be lost (cleared).
For example, assume that a prior application program issused an
Exposure Sequence (Start Exposure, Parameters, Expose Color,
Pixel Image Data for a particular color, and Terminate Exposure)
before it was interrupted by a subsequent Reset command. This
command would cancel the partially transmitted image, set all
parameters to their default values, and if possible eject or advance
the film. After the RESET command, the Digital Palette is
again ready to begin an exposure sequence.