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TS-440
S
SEMICONDUCTO
R
t
PD8251AC (Control unit IC54
)
Data bus
SN7404
5
s
5 6
•
D7o
.DI4
TX
D
Dat
a
bu
s
buffer
8_
w9
7404 2
.4576MHz
0
ra
n
m
i
buffe
r
(P
—
SI
TX
D
RX
D
P B
7
yl PD7800
E
8
R
D
W
R
SN74L5138
Ye
L
CTS
5
RTS 6 O
4
041
3
® SN7404
~
•
~
® C/D
~
RD •
•
m
~
:4~
•
C
S
l0
RESET
•p
•
CTS
:
•
DS
R
DTR
MODE
M
contro
l
R/
R
contro
l
I
ogic
R
X
RD
Y
Receiv
e
contro I
RX
C
SYNDET/B
D
Inne
r
data bus
Not us
e
Not us
e
05
(404010
pin ( Bo
rate
:
4800
)
5PD7800 INTI 12 pi
n
Not us
e
tPD8255AC-5 (Control unit IC2, 53)
I/O Port
A
I/O Port
C
I/O Port
B
Group
A
Port
A
(8 bit
)
Group
B
Port
C
(Lower 4 bit
)
R/
W
control
Group
B
Port
B
(8 bit
)
Group
A
contro
l
Dat
a
bu
s
buffer
Group
B
contro
l
74 LS 13
8
i1 At
IC2
:
Y3
I
2
ill
At IC53 Y2 I3
Basic functio
n
A
t
A
D
CS
RD
WR
Functio
n
0 0 0 0
1
Data bus °-- Port
A
0
1
0 0
1
Data bus
Port
B
1
0 0
0
1
Data bus
Port
C
0 0 0
1
0
Port A — Data bu
s
0
1
0
1
0
Port B
Data bus
1
0 0
1
0
Port C — Data bu
s
1 1
0
1
0
Control register
t—
Data bu
s
x
x
1
x x
Data bus is in high impedanc
e
statu
s
1 1
0
0
1
Combination is inhibited
"0"
shows low level (L
)
"1"
shows high level (H)
3 3