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CC>ntrol
Modem
includes
The
ACIA
peripheral
a
or
Send(CTS)
Clear
to
This
high
impedance
of
the
transmitting
active
Low
output
bit.
atatus
Send(RTS)
to
Request
The
RTS
output
the
bus.
The
data
Register
bits
CRS
is
Low(the
output
Terminal
Data
Detect(DCD)
Carrier
Data
This
high
impedance
such
in_the
as
modem
DCD
output.
a
section
of
eiver
initiates
DCD
an
of
carrier
loss
a
(CRTC
Controller)
3
CRT
(U
p i n
arrangement
ll
(GND)
Vss
RES
LPSTB
MAG
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MAI
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DISPTMG
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Voc
functions
l
severa
functions
modem.
The
compatible
TTL
communications
end
of
a
the
inhibiting
by
enables
the
MPU
to
RTF;
corresponds
output
CR6.
When
CR6=O
and
This
state).
actiire
R e a d y ( D 1 R )
compatible
TTL
of
receivingirld
a
The
DCD
input
when
the
ACIA
High.
the
interrupt
to
the
Receiver
when
EE
v
svnc
H
svmc
nm
nm
RA2
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mu
RAA
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cn
gn
oz
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so
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as
os
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27
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25
D1
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as
z
as
,
l
23
E
IEE
mw
Ell
CLK
limited
permit
that
included
CTS,RTS
are
automatic
provides
input
link
via
Transmit
Register
Data
control
peripheral
a
the
state
to
CR5
and
both
or
also
output
can
t
automatic
provides
input
communications
link
initializes
inhibits
and
transition
A
Low
to
High
indicate
the
MPU
to
Enable
Interrupt
FUNCTION
I
OF
SIGNAL
The
CRTC
provides
interface
signals
to
CRT
Interface
0
Signals
to
MPU
Bi-directional
Data
Bus
data
t B ! ' d ' e C £ I n 3 l
b
CRTC
and
ide
br;/een
remain
in
ers
an
MPU
performs
CRTC
a
Read/Write
(R/W)
/
R/W signal
controls
the
and
CRTC
MPU.
When
CRTC
transfered
MPU. When
IS
to
of MPU
is
transfered
CRTC.
to
(C_§)
Chip
Select
Select
_Chip
signal
(CS)
L o w
CSIIS
at
level,
it enables
N o f m a u l
this
ff¢5I5i¢f5-
of MPU under the condition
signal
H i g h
level.
control
of
andDCD.
control
modem
the
CTS
Empty(TDRE)
via
modem
or
of
the
Control
the
CR6=l,
RTS
be
used
for
control,
by
of
means
the
rec-
of
the
of
occurrence
bit
is
set.
LINE
13 int
'
f
al
MPU
ace
sign
to
S
d i s p l a y .
.
(D0~D.,)
b U 5 ( D o " D 1 )
used
for data transfer
are
The data bus
Ub;1PU.
outputs
high-impedance
e
state
exce
read
operation.
the
direction
of data transfer
R/W
is
at
H i g h
level,
R/W
is
L o w level data
at
is used
address
to
the
CRTC, When
R/W operation
to
CRTC inremaj
Signal
is
derived
from
decoded address
that VMA
sigial
ot'MPU
and
25
3-state
are
when
t
P
between
data of
'
is
at
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