Panasonic KX-T7440CB / KX-T7440C Service Manual ▷ View online
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9
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KX-T7440C/KX-T7440C-B
3. KEY INPUT CIRCUIT
1) Circuit Operation
The I/O ports K0~K8 of IC3 are used with alternate switching, and they are used as input ports as in the case of the key
input.
The I/O ports K0~K8 of IC3 are used with alternate switching, and they are used as input ports as in the case of the key
input.
2) Key Input Circuit
Sequential input information (negative logic) from the DSS console is executed by dynamic scanning.
The ports K0 ~ K8 of IC3 are brought to low status consecutively. If a key is pressed, the input of key-in information is
executed by ports C0 ~ C7.
Sequential input information (negative logic) from the DSS console is executed by dynamic scanning.
The ports K0 ~ K8 of IC3 are brought to low status consecutively. If a key is pressed, the input of key-in information is
executed by ports C0 ~ C7.
Circuit Diagram
62
61
60
57
56
55
54
53
52
61
60
57
56
55
54
53
52
51
50
49
48
17
16
15
14
SW1
K34
K25
K17
K9
K1
K59
K51
K43
K35
K26
K18
K10
K2
K60
K52
K44
K36
K27
K19
K11
K3
K61
K53
K45
K37
K28
K20
K12
K4
K62 / ANSWER
K65 / RELEASE
K54
K46
K38
K29
K21
K13
K5
K63
K55
K47
K39
K30
K22
K14
K6
K64
K56
K48
K40
K31
K23
K15
K7
K57
K49
K41
K32
K24
K16
K8
K66
K58
K50
K42
K33
SW2
SW3
SW4
SW5
SW6
SW7
SW8
SW9
SW18
SW17
SW16
SW15
SW14
SW13
SW12
SW11
SW10
SW26
SW25
SW24
SW23
SW22
SW21
SW20
SW19
SW35
SW34
SW33
SW32
SW31
SW30
SW29
SW28
SW44
SW43
SW42
SW41
SW40
SW39
SW38
SW37
SW53
SW52
SW51
SW50
SW49
SW48
SW47
SW46
SW62
SW61
SW60
SW59
SW58
SW57
SW56
SW55
SW71
SW70
SW69
SW68
SW67
SW66
SW65
SW64
E6
E7
E8
E9
E10
E11
E12
Q41
C0
C1
C2
C3
C4
C5
C6
C7
K[0-8]
Q40
Q39
Q38
Q37
IC3
Q36
Q35
Q34 C4
K8
K7
K6
K5
K4
K3
K2
K1
K0
K7
K6
K5
K4
K3
K2
K1
K0
C3
C2
C1
C0
C7
C6
C5
V2
V1
A1
A2
A3
A4
A5
A6
A7
A8
A9
K8
K7
K6
K5
K4
K3
K2
K1
K0
C20
R9
R8
R7
R6
R5
R4
R3
R2
R1
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KX-T7440C/KX-T7440C-B
Start Signal
18
DIN
13
32
μ
s
6.4
μ
s
DCLR
12
COUT
32
μ
s 6.4
μ
s
(19 pulses)
(47 pulses)
Acknowledge signal
4. DATA COMMUNICATION CIRCUIT
1) Function
The data communication circuit serves the following functions:
Information exchanger between DSHS and DSS console, key input information as well as data for the LED control, etc.
This information is continuously at times.
The data communication circuit serves the following functions:
Information exchanger between DSHS and DSS console, key input information as well as data for the LED control, etc.
This information is continuously at times.
2) Circuit Operation
When the DSS console receives an IRQ signal from the DSHS and after sending the key input information (19 pulses) to the
DSHS and receiving data (47 pulses) for LED control, etc. The DSS console will return to the DSHS an acknowledge signal.
When the DSS console receives an IRQ signal from the DSHS and after sending the key input information (19 pulses) to the
DSHS and receiving data (47 pulses) for LED control, etc. The DSS console will return to the DSHS an acknowledge signal.
3) Reception
The data from the DSS console is received via the H and L line along the path shown below.
H, L Line
The data from the DSS console is received via the H and L line along the path shown below.
H, L Line
→
D1
→
T1
→
R49
→
Q43
→
IC2
→
IC3
18
4)Transmission
The data to the DSS console is transmitted along the following path.
IC3
The data to the DSS console is transmitted along the following path.
IC3
12
→
IC2
→
R45
→
Q44
→
T1
→
P1
→
H, L line.
Timing Chart
Circuit Diagram
12
19
18
13
V1(+5V)
1
1
1
2
2
3
13
12
12
11
9
8
8
10
5
6
6
4
10
9
4
5
7
6
1
2
4
4
1
H
L
1
3
2
3
2
G
O
I
3
O
I
G
2
V2(+5V)
IC1
D1
+ ~
~
–
JP2
L1
JP3
V1
R46
R45
V1
V1
C4
R47
Q44
Q43
T1
R51
R56
R49
R48
IC2
IC2
IC2
R44
R43
C3
R50
D73
C5
IC2
DOUT
DINT
IC3
DIN
DCLR
JK1
IC4
C8
C7
C6
C1
1
C10
C9
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KX-T7440C/KX-T7440C-B
48
17
16
15
14
17
16
15
14
47
46
45
44
43
42
41
40
39
38
37
36
35
34
R24
R31
R32
R33
R34
R35
R36
R37
R25
R26
R27
C17
R28
R29
IC3
R30
V1
B15
B16
B17
B18
B19
B20
B21
B22
B23
B24
B25
B26
B27
B28
E6
E7
CCC[0]
CCC[1]
CCC[2]
CCC[3]
CCC[4]
E8
E9
E10
V2
C20
V2
G
D41
R
G
D46
R
G
D51
R
G
D56
R
G
D61
R
G
D66
R
G
D40
R
G
D45
R
G
D50
R
G
D55
R
G
D60
R
G
D65
R
G
D39
R
G
D44
R
G
D49
R
G
D54
R
G
D59
R
G
D64
R
G
D38
R
G
D43
R
G
D48
R
G
D53
R
G
D58
R
G
D63
R
G
D37
LL[14]
LL[15]
LL[16]
LL[17]
LL[18]
LL[19]
LL[20]
LL[21]
LL[22]
LL[23]
LL[24]
LL[25]
LL[26]
LL[27]
LL[14]
LL[15]
LL[16]
L[14]
L[15]
L[16]
L[17]
L[18]
L[19]
L[20]
L[21]
L[22]
L[23]
L[24]
L[25]
L[26]
L[27]
LL[17]
LL[18]
LL[19]
LL[20]
LL[21]
LL[22]
LL[23]
LL[24]
LL[25]
LL[26]
LL[27]
C[4]
C[3]
C[2]
C[1]
C[0]
V2
Q21
Q28
Q34
Q35
Q36
Q37
Q38
Q27
Q26
Q25
Q24
Q23
Q22
Q20
Q19
Q18
Q17
Q16
Q15
R
G
D42
R
G
D47
R
G
D52
R
G
D57
R
G
D62
R
G
D67
R
5. LED CIRCUIT
Circuit Diagram
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KX-T7440C/KX-T7440C-B
6. LED CIRCUIT KEY INPUT CIRCUIT
1) Circuit Operation
A drive pulse wave, as in Fig. 1, is output by IC3. That signal goes through the drive digital transistor and connects the key
button and LED cathode. By pressing the key, the drive pulse wave is input to the keyboard. In order to light the appropriate
LED, the LED control port is turned ON. That result LED is lit by the pulse driver.
A drive pulse wave, as in Fig. 1, is output by IC3. That signal goes through the drive digital transistor and connects the key
button and LED cathode. By pressing the key, the drive pulse wave is input to the keyboard. In order to light the appropriate
LED, the LED control port is turned ON. That result LED is lit by the pulse driver.
5V
LED
ON/OFF
CONTROL
ON/OFF
CONTROL
PULSE
OUTPUT
OUTPUT
KYE
INPUT
INPUT
LED
L [0] ~ L [27]
C [0] ~ C [7]
K [0] ~ K [8]
IC3
A
B
C[0]
C[1]
C[2]
C[3]
A Each Cannel's Pulse Output
Fig. 1
Fig. 2
A and B 's Wave
Circuit Diagram
A
B
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