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2-3-14
(2) Operation unit right PCB
TB
Operation
unit
main
PCB
CNB-1
CNB-2
CNB-3
CNB-4
CNB-5
CNB-6
CNB-7
CNB-8
CNB-13
CNB-14
R17
R7
R8
TR4
R18
R19
R20
CNB-10
CNB-9
CNB-12
CNB-11
N.C.
DIGKEY R1
KEY8
KEY9
KEY10
KEY11
D4 D5 D6 D7
KEY12
KEY13
KEY14
KEY15
KEY16
KEY17
KEY18
KEY19
KEY20
KEY21
KEY22
KEY23
DIGKEY R2
DIGKEY R3
DIGKEY R4
SCAN R1
SCAN R2
SCAN R3
SCAN R4
BUZZER
BZ
5 V
DIGLED R2
DIGLED R1
LED17
LED18
LED19
LED20
DIGLED R4
DIGLED R3
Figure 2-3-10 Operation unit right PCB block diagram
The operation unit right PCB (ORPCB) consists of key switches and LEDs. Depending
on the scan signals (SCAN R1 - R4) and the LED lighting selection signals (DIGLED R1
- R4) received from the operation unit main PCB (OMPCB), the LED to be lit is selected,
and the key switch pressed is identified by the scan signals (SCAN R1 - R4) and the
return signals (DIGKEY R1 - R4).
As an example, to light LED17, the LED lighting selection signal (DIGLED R1) should
be driven low in synchronization with a low level on the scan signal (SCAN R1).
Transistor TR4 conducts and LED17 is lit. LEDs can be lit dynamically by repeating
such operations.
As an example, if KEY8 is pressed, the corresponding key switch is turned on feeding
the low level of the scan signal back to the operation unit main PCB (OMPCB) via the
return signal (DIGKEY R1). The operation unit main PCB (OMPCB) locates the position
where the line outputting the scan signal and the line inputting the return signal cross,
and thereby determines which key switch was operated.
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