2C9
2-3-14
2-3-4 Operation unit PCB
Figure 2-3-7Operation unit PCB block diagram
The operation unit PCB (OPPCB) consists of key switches, LEDs, 7 segment LED and buzzer. The lighting of LEDs is
determined by scan signals (SCAN0 to SCAN7) and LED lighting selection signals (LED0 to LED12) from the main PCB
(MPCB). The key switches operated are identified by the scan signals (SCAN0 to SCAN7) and the return signals (KEY0 to
KEY4).
As an example, to light L1, the LED lighting selection signal (LED0) should be driven low in synchronization with a low
level on the scan signal (SCAN0). LEDs can be lit dynamically by repeating such operations.
As another example, if K1 is pressed, the corresponding key switch is turned on feeding the low level of the scan signal
(SCAN0) back to the main PCB (MPCB) via the return signal (KEY0). The main PCB (MPCB) 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.
K5
K10
K15
K20
K25
K30
K38
K4
K9
K14
K19
K24
K29
K37
K34
K3
K8
K13
K18
K23
K28
K36
K33
K2
K7
K12
K17
K22
K27
K32
K1
K6
D1
+5V
+5V
BUZERDRN
SCAN7N
SCAN6N
SCAN5N
SCAN4N
SCAN3N
SCAN2N
SCAN1N
SCAN0N
10
9
8
7
6
5
4
3
2
1
f1
f2
f3
g1
g2
g3
DP1
DP2
DP3
Dig1
Dig1
Dig2
Dig3
27
23
17
28
22
12
5
9
14
3
26
19
18
e3
e2
e1
d3
d2
d1
c3
c2
c1
b3
b2
b1
a3
a2
a1
10
6
1
11
7
2
13
8
4
15
20
24
16
21
25
KEY4
KEY3
KEY2
KEY1
KEY0
LED12
LED11
LED10
LED9
LED8
LED7
LED6
LED5
LED4
LED3
LED2
LED1
LED0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
BZ1
YC1
U1
SW
LED
7 segment
YC2
2
1
K11
K16
K21
K26
K35
K31
D2
2
1
D3
2
1
D4
2
1
D5
2
1
D6
2
1
D7
2
1
D8
2
1
L9
L18
L27
L36
L46
L37
L75
L55
L64
L73
L8
L17
L26
L35
L45
L54
L63
L72
L7
L16
L25
L34
L44
L53
L62
L71
L6
L15
L24
L33
L43
L52
L61
L70
L5
L14
L23
L32
L42
L51
L60
L69
L13
L22
L31
L41
L50
L59
L68
L3
L12
L21
L30
L40
L49
L58
L67
L2
L11
L20
L29
L39
L48
L66
L1
L10
L19
L28
L38
L47
L56
L65
L74
Summary of Contents for CS-1620
Page 1: ...SERVICE MANUAL Published in June 05 2C970946 Revision 6 CS 1620 2020...
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