31 August 1989
10.8 PAPER SIZE SENSORS
The CPU sends separate scan pulses (SCAN 1, 2, 3, and 4) to the corresponding sensors in
each cassette. The output of this group of sensors for all cassettes can be monitored by one
data bus because the scan pulses are sequential. This allows the CPU to determine which
cassette the information comes from.
In the above diagram, two example actuator plates are shown for paper size sensors 1 and 2.
The actuator plates in cassette 1 and cassette 2 have notches in the fourth and second
positions respectively. The photointerrupters corresponding to the notches remain active (0
volts). Thus, when scan line 1 is high, bit 4 of the data bus remains LOW; when scan line 2 is
high, bit 2 of the data bus remains LOW. The CPU monitors the data bus at the appropriate
time to determine the paper size in cassettes 1 and 2.
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