A SERVICE OF

logo

15
P1
A11
AEN
WR/
RD/
B4
D3
D5
A8
A6
A4
AEN
A3
A5
A7
A9
2
4
6
8
11
13
15
17
P0
P1
P2
P3
P4
P5
P6
P7
U1
A9
A8
A7
A6
A5
A4
A3
15
13
11
10
12
14
16
SW1
SW1
SW1
SW1
SW1
SW1
SW1
2
4
6
7
5
3
1
P1
P1
P1
P1
P1
P1
P1
A22
A23
A24
A25
A26
A27
A28
P1
P1
P1
P1
B2
A31
A30
A29
P1
P1
B13
B14
RESET
A0
A1
A2
D0
D1
D2
D3
D4
D5
D6
D7
A9
A8
A7
A6
A5
A4
A3
A2
P1
P1
P1
P1
P1
P1
P1
P1
P1
P1
P1
P1
P2
P2
P1
P2
P2
B21
D4
D6
B25
B24
B23
IRQ10
IRQ12
IRQ2
IRQ3
IRQ4
IRQ5
IRQ7
IRQ11
IRQ15
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
3
5
7
9
12
14
16
18
GND
74LS682
GND
GND
VDO
P=Q
P>Q
VSS
R1
20
19
1
10
+5V
+5V
12
98SW1
A8
A6
A4
AEN
A3
A5
A7
A9
2
4
6
8
11
13
15
17
P0
P1
P2
P3
P4
P5
P6
P7
U2
15
13
11
10
12
14
16
SW2
SW2
SW2
SW2
SW2
SW2
SW2
2
4
6
7
5
3
1
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
3
5
7
9
12
14
16
18
GND
74LS682
GND
GND
VDO
P=Q
P>Q
VSS
R2
20
19
1
10
+5V
+5V
12
98SW2
1
74LS125A
R5
U6
GND
23
4
74LS125A
U6
GND
56
1
2
+5V
U3
13
74LS125A
U6
1211
10
74LS125A
U6
98
E1
2
4
6
8
10
12
14
16
18
1
3
5
7
9
11
13
15
17
E2
2
4
6
8
10
12
14
16
18
1
3
5
7
9
11
13
15
17
R3
1
2
GND
D1
12
E9
4
3
2
1
R4
1
2
GND
D2
12
E10
4
3
2
1
P1
P1
P1
B9
B3
B29
+12V
+5V
+5V
+5V
RP1
1
6
RP1
1
2
RP1
1
4
U12
74LS245
A2
A3
A4
A5
A6
A7
A8
3
4
5
6
7
8
9
B2
B3
B4
B5
B6
B7
B8
17
16
15
14
13
12
11
BD1
BD2
BD3
BD4
BD5
BD6
BD7
A1
2
B1
18 BD0
GND
+5V
SHEET 1
10
20
1
19
VSS
VDO
DIR
G
BRD
U3
HC244
A1
A2
A3
A4
11
13
15
17
Y1
Y2
Y3
Y4
9
7
5
3
BWR/
BRD/
GND
10
19
VDO/VSS
G
GND
HC244
A1
A2
A3
A4
2
4
6
8
Y1
Y2
Y3
Y4
18
16
14
12
BRESET
BA0
BA1
BA2
+5V
20
1
VDO/VSS
G
+12V
+5V
GND
P1
P1
B1
B31
GND
GND
1
2
C10
C8
1
2
3
C1
1
2
3
C4
1
2
3
C5
1
2
3
C2
1
2
3
C3
1
2
3
P1
B7
-12V
-12V
+5V
GND
C9
1
2
3
C7
1
2
3
C6
1
2
3
U4
8250A
D0
D1
D2
D3
D4
D5
D6
D7
DTR
RTS
OUT1
OUT2
CSOUT
DDIS
BAUDOUT
INTRPT
SOUT
1
2
3
4
5
6
7
8
33
32
34
31
24
23
15
30
11
XTAL1
XTAL2
MR
CS0
CS1
CS2
DISTR
DISTR
DOSTR
DOSTR
ADS
RCLK
SIN
CTS
DSR
DCD
RI
A0
A1
A2
16
17
35
12
13
14
22
21
19
18
25
9
10
36
37
38
39
28
27
26
BD0
BD1
BD2
BD3
BD4
BD5
BD6
BD7
GND
+5V
20
40
VSS
VDO
GND
+5V
BRESET
BRD/
BWR/
BA0
BA1
BA2
RD1
CTS1
DSR1
DCD1
RI1
SHEET 2
SHEET 2
SHEET 2
DTR1
RTS1
TD1
U5
8250A
D0
D1
D2
D3
D4
D5
D6
D7
DTR
RTS
OUT1
OUT2
CSOUT
DDIS
BAUDOUT
INTRPT
SOUT
1
2
3
4
5
6
7
8
33
32
34
31
24
23
15
30
11
XTAL1
XTAL2
MR
CS0
CS1
CS2
DISTR
DISTR
DOSTR
DOSTR
ADS
RCLK
SIN
CTS
DSR
DCD
RI
A0
A1
A2
16
17
35
12
13
14
22
21
19
18
25
9
10
36
37
38
39
28
27
26
BD0
BD1
BD2
BD3
BD4
BD5
BD6
BD7
GND
+5V
20
40
VSS
VDO
GND
+5V
BRESET
BRD/
BWR/
BA0
BA1
BA2
RD2
CTS2
DSR2
DCD2
RI2
SHEET 2
SHEET 2
SHEET 2
DTR2
RTS2
TD2
GND
+5V
VSS
VDO
TXCO
NC
OUT
Y1
114
78
APPENDIX: Circuit-Board Design