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Pin
Name
I/O
49 RD
O Read signal output terminal.
50 WT
O Write signal output terminal.
51 P35
I/O P35 signal input/output terminal.
52 P34
I/O P34 signal input/output terminal.
53 P33
I/O P33 signal input/output terminal.
54 P32
I/O P32 signal input/output terminal.
55 P31
I/O P31 signal input/output terminal.
56 P30
I/O P30 signal input/output terminal.
57 Vcc
– Power supply terminal.
58 P71
I/O P71 signal input/output terminal.
59 P70
I/O P70 signal input/output terminal.
60 P67
O STB signal output terminal.
61 P66
O Serial Clock Pulse output terminal.
62 P65
O Serial Data output terminal.
63 P64
O DATA output terminal.
64 P63
I/O P63 signal input/output terminal.
1.21.
IC905 and IC912 on the Main Board are using the
Octal 3-State D-FFs IC MC74HC374AF.
Description of this IC is as follows:
OC
1
1Q
2
1D
3
2D
4
2Q
5
(TOP VIEW)
3Q
6
3D
7
4D
8
4Q
9
GND 10
Truth Table
OC
CLK
L
L
L
∗
H
∗
: Don't care.
Z : High Impedance
Description
20 Vcc
19 8Q
18 8D
17 7D
16 7Q
15 6Q
14 6D
13 5D
12 5Q
11 CLK
D
OUTPUT (Q)
H
H
L
L
∗
No Change
∗
Z
1.22.
IC844 and IC903 on the Main Board are using the
Hex D-FFs IC MC74HC174AF.
Description of this IC is as follows:
CLEAR 1
1Q 2
1D 3
2D 4
2Q 5
3D 6
3Q 7
GND 8
Truth Table
INPUTS
D
CLR
∗
L
H
L
H
H
∗
H
∗
: Don't care.
1.23.
IC901 on the Main Board is using the Quad 2-Input
NAND Gates IC YWMC74HC00AF.
Description of this IC is as follows:
1A 1
1B 2
1Y 3
2A 4
2B 5
2Y 6
GND 7
Truth Table
INPUTS
A
B
L
L
L
H
H
L
H
H
28
16 Vcc
15 6Q
14 6D
13 5D
(TOP VIEW)
12 5Q
11 4D
10 4Q
9 CLK
OUTPUTS
Function
CLK
Q
Q
∗
L
H
Clear
L
H
H
L
Qn
Qn
No Change
14 Vcc
13 4B
12 4A
11 4Y
10 3B
9 3A
8 3Y
(TOP VIEW)
OUTPUT
Y
H
H
H
L
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