Wersi CD 600, Assembly Manual

Page: 64 / 98

AM 320-01-808
64
4. CB 41, CB 42, CB 43 (Main Control Panels
Left, Center, Right)
These boards carry the switch recognition and the activaing
of the LEDs. Furthermore, the CB 42 carries the
LCD display plus outputting IC 1 (HC 174). And on the
CB 43 there is the on/off switch with integrated bi-color
LED.
The switches (and their appropriate LEDs) are arranged in
5 groups with 24 switches each. If no switch is depressed,
both the SENSE and the KD output of the respective pair of
comparators are set to +5 V.
A momentary switch closure results in a Sense and
KD pulse, which is applied to the CPU's data
bus. This sense pulse occupies a specific time
slot in the CPU's sequence program and
instructs the CPU to initiate the function for
that time slot. The CPU, in turn, sends a
serial data code to the appropriate shift
register (74 HCT 164), designating the LEDs
to light up.