TM 5-6675-316-14
(1) Variator or enlarging lens control. This circuit operates in a similar
fashion to the font row shift control. The start control circuit initializes the
sequence of events when a START command is received from the program. The amount of
movement, or number of motor steps required, already has been passed to the start-
stop-step-delay logic. The START control releases an INHIBIT signal to the start-
stop-step-delay control placing it in the stepping mode. At the same time, the sync
control is enabled allowing 500 Hz pulses to be fed to the motor sequencer. The
direction in which the lens is to move was passed from the program in code to the
FORWARD/REVERSE DECODE logic, and from there to the motor sequencer. The motor se-
quencer now commences to output drive signals to the motor via the main driver board.
Each time that the motor steps, the total step count, as set by the program, is
decreased by one. As the last pulse is reached, the start-stop-delay logic inhibits
further pulse action by stopping the sync control. At this point, the stop-start-
delay logic goes into the delay mode, and begins to count the 1 kHz pulse output of
the sync control. When the required delay is reached (1 pulse = 1 msec), the logic
generates a DELAY COMPLETE pulse, and places the entire logic block into a WAIT
condition. The START CONTROL logic informs the program of this condition via the
INPUT/OUTPUTj logic and the data bus. Other information passed via the INPUT/OUTPUT
logic covers the condition of the collimator and leading motors.
(2) Collimator lens control. This is nearly identical to the preceding control
description, the only difference being the functional description of the STOP and
START commands from the program.
(3) Leading motor. This circuit is similar to the VARIATOR and COLLIMATOR cir-
cuits; there are two differences:
(a) Power to the leading motor is not shut off at the end of the STEP/
DELAY sequence. At the completion of movement, the driver board holds 50-percent
power to the motor coils. This ensures that the film or paper maintains its
position.
(b) The leading motor mechanism has a film out switch which passes this
information to the program via the data bus.
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