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APPENDIX: Circuit-Board Design
A22
A23
A24
A25
A26
A27
A28
A11
A9
A8
A7
A6
A5
A4
A3
AEN
A8
A6
A4
AEN
A3
A5
A7
A9
RESET
A0
A1
A2
2
4
6
8
GND
1
VDO/VSS
A1
A2
A3
A4
Y1
Y2
Y3
Y4
G
74LS244
11
13
15
17
GND
19
VDO/VSS
A1
A2
A3
A4
Y1
Y2
Y3
Y4
G
U5
74LS244
20
+5V
10
GND
WR/
RD/
9
7
5
3
BWR/
BRD/
GND
15
13
11
10
12
14
16
PORT 1
GND
3
5
7
9
12
14
16
18
U5
U1
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
VSS
P>Q
1
10
GND
74LS682
P=Q
VDO
2
4
6
8
11
13
15
17
P0
P1
P2
P3
P4
P5
P6
P7
GND
15
13
11
10
12
14
16
SW2
SW2
SW2
SW2
SW2
SW2
SW2
2
4
6
7
5
3
1
PORT 2
GND
3
5
7
9
12
14
16
18
U4
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
VSS
P>Q
1
10
GND
74LS682
P=Q
VDO
A8
A6
A4
AEN
A3
A5
A7
A9
SW1
9
8
20
19
+5V
18
16
14
12
BRESET
BA0
BA1
BA2
R1
12
Y1
+5V
20
R2
19
8SW2 9
2
1
+5V
VDO
OUT
+5V
1
7
14
8
GND
TXCO
U2
+5V
GND
U3
VDO
VSS
+5V
GND
40
20
XTAL1
XTAL2
MR
CS0
CS1
CS2
DISTR
DISTR
DOSTR
DOSTR
ADS
RCLK
SIN
CTS
DSR
DCD
RI
A0
A1
A2
D0
D1
D2
D3
D4
D5
D6
D7
DTR
RTS
OUT1
OUT2
CSOUT
DDIS
BAUDOUT
INTRPT
SOUT
GND
+5V
BRESET
BRD/
BWR/
RD1
CTS1
DSR1
DCD1
RI1
BA0
BA1
BA2
8250A
U7
1
2
GND
3
74LS125A
+5V
12
R3
P1
P1
P1
P1
P1
P1
P1
P1
19
1
BRD/
3
4
5
6
7
8
9
2
D0
D1
D2
D3
D4
D5
D6
D7
G
DIR
A1
A2
A3
A4
A5
A6
A7
A8
74LS245
B2
B3
B4
B5
B6
B7
B8
B1
U7
5
6
4
74LS125A
GND
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
DTR1
RTS1
TD1
8250A
U6
VDO
VSS
+5V
GND
17
16
15
14
13
12
11
10
18
20
DB1
DB2
DB3
DB4
DB5
DB6
DB7
DB0
E2
E1
2
E4
E3
U7
8
D2
3
11 2
2
4
6
8
10
12
14
16
2
P2
D6
IRQ15
IRQ10
IRQ11
IRQ12
IRQ2
IRQ3
IRQ4
IRQ5
10
9
74LS125A
3
1
1
D1
2
R5
R4
12
GND
12
GND
16
17
35
12
13
14
22
21
19
18
25
9
10
36
37
38
39
28
27
26
13
12
U7
74LS125A
B1
B31
P1
P1
16
15
14
13
12
11
10
9
VSS VEE-
MC145406
U8
3
6
8
11
OUTA
OUTB
OUTC
OUTD
V+
ENA
INA
ENB
INB
ENC
INC
END
IND
GND
MC1489
+12
-12V
+5V
+5V
+12V
-12V
C8
C9 C6 C1 C2 C3 C4
C5 C7
+
111111111
22
3
+5V
GND
GND
B9
B7
B3
B29
P1
P1
P1
P1
VDO VEE+
+12V
+5V
TD2
RTS2
DTR2
GND
-12V
RD2/
RD2/
TD2/
TD2/
CTS2/
CTS2/
RTS2/
RTS2/
DSR2/
DSR2/
DTR2/
DTR2/
+12V
U9
14
2
1
5
4
9
10
12
13
7
GND
2
4
6
8
11
13
15
17
P0
P1
P2
P3
P4
P5
P6
P7
SW1
SW1
SW1
SW1
SW1
SW1
SW1
2
4
6
7
5
3
1
B2
A31
A30
A29
P1
P1
P1
P1
B13
B14
P1
P1
A9
A8
A7
A6
A5
A4
A3
A2
P1
P1
P1
P1
P1
P1
P1
P1
B4
B25
B24
B23
P1
P1
P1
P1
D3
D4
D5
P2
P2
P2
2
3
3
2
8
5
7
4
6
6
4
20
J1
J4
J1
J4
J1
J4
J1
J4
J1
J4
J1
J4
DCD2/
DCD2/
RI2/
RI2/
DCD1/
DCD1/
RI1/
RI1/
1
8
9
22
1
1
9
9
J1
J4
J1
J4
J2
J3
J2
J3
RD1/
RD1/
TD1/
TD1/
CTS1/
CTS1/
RTS1/
RTS1/
DSR1/
DSR1/
DTR1/
DTR1/
2
2
3
3
8
8
7
7
6
6
4
4
J2
J3
J2
J3
J2
J3
J2
J3
J2
J3
J2
J3
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VSS VEE-
MC145406
U10
VDO VEE+
+12V
+5V
TD1
RTS1
DTR1
GND
-12V
1
2
3
4
5
6
7
8
NC
VSS
2
3
2
3
2
3
2
3
2
3
2
3
2
3
1
2
3
4
5
6
7
8
33
32
34
31
24
23
15
30
11
VDO
VSS
40
20
XTAL1
XTAL2
MR
CS0
CS1
CS2
DISTR
DISTR
DOSTR
DOSTR
ADS
RCLK
SIN
CTS
DSR
DCD
RI
A0
A1
A2
D0
D1
D2
D3
D4
D5
D6
D7
DTR
RTS
OUT1
OUT2
CSOUT
DDIS
BAUDOUT
INTRPT
SOUT
GND
+5V
BRESET
BRD/
BWR/
RD2
CTS2
DSR2
DCD2
RI2
BA0
BA1
BA2
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
DTR2
RTS2
TD2
16
17
35
12
13
14
22
21
19
18
25
9
10
36
37
38
39
28
27
26
1
2
3
4
5
6
7
8
33
32
34
31
24
23
15
30
11
11
1
3
5
7
9
11
13
15
2
4
6
8
10
12
14
16
1
3
5
7
9
11
13
15