Service manual

TC74VHCT245AFT (XT744A00)
TC74VHC245FT (XU797A00)
Octal 3-State Bus Transceiver
CPU:
CNV:
TC74HC251AF (XQ968A00)
3-State 8 to 1 Data Selector
CPU: IC160
HD74LV393AFPEL (IS039300)
Dual 4-Bit Binary Counter
CPU: IC302
HD74LVC540AT (XZ512A00)
Bus Buffer
CNV: IC17
TC74VHCT574AFT (XY059A00)
Octal D-Type Flip-Flop
CPU: IC161, 162
SN75124N (XE737A00)
Line Receiver
CPU: IC144
TC74LVXC3245FS (XY907A00)
Dual Supply Octal Bus Transceiver
CPU: IC127–131
SN75C1168NSR (XU073A00)
Line Driver/Receiver
CPU: IC125, 142
1
2
3
4
5
6
7
20
19
18
17
16
15
14
Vcc
G
B1
B2
B3
B4
B5
B6
B7
B8
8
9
10
12
11
GND
A8
A7
A6
A5
A4
A3
A2
A1
D1R
13
IC119, 120, 123, 155, 165–168, 170
172–174, 179–184
IC23–34
10
9
8
7
6
5
4
3
2
1
D5
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D
CK
Q
OE
D6
D7
GND
D4
D3
D2
D1
D0
Output
Control
Q5
Q6
Q7
Clock
Q4
Q3
Q2
Q1
Q0
Vcc
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
3
2
1
Y
W
STROBE
GND
0
16
15
14
13
12
11
Vcc
4
5
6
7
A
B
8
9
10
C
DATA
INPUTS
DATA
SELECT
DATE
INPUTS
OUTPUTS
D4
D5
B
C
S
D7
A
D6
D2 D3
D1
D0
Y
W
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
Vcc
GND
INPUTS
OUTPUTS
FUNCTION
G
L
L
H
DIR A-BUS B-BUS
L
H
X
A=B OUTPUT INPUT
B=A INPUT OUTPUT
Z High lmpedance
X : Don't Care
Z : High lmpedance
VCCA
DIR
A1
A2
A3
A4
A5
A6
A7
A8
GND
GND
V
CCB
NC
G
B1
1
3 EN2 (AB)
3 EN1 (BA)
G3
2
B2
B3
B4
B5
B6
B7
B8
GND
(TOP VIEW)
1
2
3
4
5
6
7
8
9
10
11
12
15
14
13
18
17
16
21
20
23
24
22
19
B1
21
V
CCA VCCB
B8
14
131211
1
2DIR
22G
10A8
3A1
Logic
Level
Converter
Same as above block
24
1A
1B
2R
2S
2A
2B
2Y
GND
1 16
2 15
3 14
4 13
5 12
6 11
7 10
8 9
Vcc
1S
1R
1Y
3A
3S
3R
3Y
1
2
3
4
5
6
7
1B
1A
1R
1DE
2R
2A
2B
16
15
14
13
12
11
10
Vcc
1D
1Y
1Z
2DE
2Z
2Y
8
GND
9
2D
1
2
3
4
5
6
7
1A
1 CLEAR
1QA
1QC
1QD
Vss
(GND)
1QB
14
13
12
11
10
9
VDD (Vcc)
2A
2 CLEAR
2QA
2QB
2QC
2QD
8
CL
QA
QB
QC
A
QD
CL
QA
QB
QC
A
QD
SREV1
25