Repair manual

2-50
THEORY OF OPERATION
Note
If the film parameter specified by the Expose
Color command (set by the host computer software)
is inappropriate for the attached camera, the Digital
Palette will not allow a picture or slide to be taken.
The film parameter appropriate for the attached
camera must be set by the host computer software.
2) Film Advance
The Camera Back Control circuit (Figure 2-9, sheet 5) is also
responsible for the film advance functions associated with a typical
exposure sequence:
o Opens and closes the attached camera shutter.
o Ejects the exposured film frame for a non-motorized camera
back (Pack Film and 4 x 5). For non-motorized camera backs,
the user must manually remove the ejected film frame.
o Advances the exposed film frame for a motorized camera back
(35mm and Auto Film)
The Camera Back Control circuit, in conjunction with the
microprocessor network, controls the film advance functions.
Before an exposure takes place, the Expose Color command is sent
by the host computer via the applicable parallel interface to the
Digital Palette buffer memory. Upon receipt of this command, the
microprocessor network removes and executes the Expose Color
command from the buffer memory. The microprocessor network
decodes the Expose Color command and then flags the film
advance instructions from the EPROM. The EPROM applies the
film advance instructions to the input of the microprocessor net
work via the Address/Data communications bus. The
microprocessor network decodes the film advance instructions
from the EPROM and then applies the film advance data via the
Address/Data communications bus to the octal addressable latch in
the camera back drive network.
At the appropriate time in the exposure sequence (start of
exposure), the octal addressable latch outputs the camera advance
(CADVANCE) signal to the camera back drive network. The
camera back drive network applies the CADVANCE signal via
connector J11 to the attached camera back. This signal causes the