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