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1.24.
IC911 on the Main Board is using the Octal 3-State
Bus Transceiver IC MC74HC245AF.
Description of this IC is as follows:
DIR
1
A1
2
A2
3
A3
4
A4
5
(TOP VIEW)
A5
6
A6
7
A7
8
A8
9
GND 10
Truth Table
INPUTS
DIR
ENABLE G
H
L
L
L
∗
H
∗
: Don't care.
1.25.
IC848 on the Main Board is using the Quad 2-Input
NAND Schmitt Trigger Gates IC MC74HC132AF.
Description of this IC is as follows:
1A 1
1B 2
1Y 3
2A 4
2B 5
2Y 6
GND 7
(TOP VIEW)
Truth Table
INPUTS
OUTPUT
Y
A
B
H
L
L
H
L
H
H
H
L
L
H
H
20 Vcc
19 ENABLE G
18 B1
17 B2
16 B3
15 B4
14 B5
13 B6
12 B7
11 B8
FUNCTION
A
B
B
A
A
OFF
B
14 Vcc
13 4B
12 4A
11 4Y
10 3B
9 3A
8 3Y
1.26.
IC846 on the Main Board is using the Quad 2-Input
NOR GAtes IC YWMC74HC02AF.
Description of this IC is as follows:
1Y 1
1A 2
1B 3
2Y 4
2A 5
2B 6
GND 7
Truth Table
INPUTS
A
B
L
L
L
H
H
L
H
H
1.27.
IC917 on the Main Board is using the Synchronous
Presettable Binary Counter with Clear IC MC74HC
161AF.
Description of this IC is as follows:
CLEAR 1
CLK 2
A 3
B 4
C 5
D 6
ENABLE P 7
GND 8
Truth Table
INPUTS
Clear Load CLK
H
H
H
L
∗
∗
∗
∗
H
∗
: Don't care.
29
14 Vcc
13 4Y
12 4B
11 4A
10 3Y
9 3B
8 3A
(TOP VIEW)
OUTPUT
Y
H
L
L
L
16 Vcc
15 RIPPLE CARRY
14 Q
A
13 Q
B
(TOP VIEW)
12 Q
C
11 Q
D
10 ENABLE T
9 LOAD
OUTPUTS
Enable
Ripple
Q
Q
Q
Q
A
B
C
D
Carry
P
T
H
H
∗ ∗
D
D
D
D
A
B
C
D
∗ ∗
L
L
L
L
∗
H
H
H
H
H
Function
Count
Data Set
Clear
–
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