Casio QT-2100 Service Manual page 66

10. HD74LVC138 (IC21)
1
A
A
2
B B Y
0
Y
3 C
C
1
Y
G 4 G
2
2A 2A
Y
G G
5
3
2B 2B
Y
6
G G
4
1 1
Y 7 Y Y Y
7 7 6 5
GND 8
11. HD74LVC244 (IC3,5)
1G 1
1A1 2
2Y4 3
1A2
4
2Y3
5
1A3 6
2Y2 7
1A4 8
2Y1 9
GND 10
13. LC35256FT (IC1)
A14 1 28 Vcc
A12 2 27
WE
A7 3 26 A13
A6 4 25 A8
A5 5 24 A9
A4 6 23 A11
A3 7 22
OE
A2 8 21 A10
A1 9
20 CE
A0 10
19 I/O8
I/O1 11 18 I/O7
I/O2 12 17 I/O6
I/O3 13 16 I/O5
GND 14 15 I/O4
16 V
CC
Enable
15 Y
0
G G
1 2A
14 Y
X X
1
X H
13
Y
2
L X
12 Y
3 H L
H L
11 Y
4
H L
10 Y
5
H L
H L
9 Y
6
H L
H L
H L
H: High
L: Low
X: Don t care
20 V
CC
19
2G
18
1Y1
17 2A4
16 1Y2
15 2A3
14 1Y3
13 2A2
12
1Y4
11
2A1
A0 ~ A14
ADDRESS
DECODER
BUFFER
I/O1 ~ I/O8
OUTPUT
BUFFER
INPUT
BUFFER
CE
WE
OE
Inputs
Select
G C B A Y
2B 0
H X X X H
X X X X H
X X X X H
L L L L L
L L L H H
L L H L H
L L H H H
L H L L H
L H L H H
L H H L H
L H H H H
12. HD74LVC245 (IC2,6)
1 20
T/R Vcc
2 19
A0 OE
3 18
A1 B0
4 17
A2 B1
5 16
A3 B2
6 15
A4 B3
7 14
A5 B4
8 13
A6 B5
9 12
A7 B6
10 11
GND B7
MEMORY
Vcc
ARRAY
GND
LOGIC
DATA
CONTOROL
CIRCUIT
CONTOROL
CIRCUIT
— 64 —
Outputs
Y Y Y Y Y
1 2 3 4 5
H H H H H
H H H H H
H H H H H
H H H H H
L H H H H
H L H H H
H H L H H
H H H L H
H H H H L
H H H H H
H H H H H
Inputs
Output Y
OE T / R
L L Bus B Data to Bus A
L H Bus A Data to Bus B
H X
H : High
L : Low
X :
Don t care
Z :
High impedance
Y Y
6 7
H H
H H
H H
H H
H H
H H
H H
H H
H H
L H
H L
Z