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MZ3500
6-3. Block diagram
of the
interface
Control
signal
Peripheral
6-4. System switch
functions
SW5
SW6
SW7
ON
Causes
an
error when
the
ER
signal
is low or
open
during data
output.
Always
high when power
is
on
to the
main
unit.
Causes
on
error when
the
PO
signal
is
high
during
data
output.
OFF
ER
signal
is
disabled.
The CD
signal
is set
high
while
data
output,
but
would
not be set
high
when
the
echo-back
function
is
selected
for
the
host
computer.
Polarity
is
inverted.
6-5.
8251AC
controls
There
are two
control
words
for the
8251
AC.
(1)
Mode instruction: Defining
general
operational
para-
meters,
such
as
unit,
stop bit, etc.
(2)
Command instruction: Defining
status
words
used
for
actual
operation,
such
as
send/receive enable, etc.
1)
Definition
of
generation operational parameters
•
Baud rate
•
Character
size
•
Even/odd/off parity
assignment
••Stop
bit
size
"Corresponds
to
channel command
of
BASIC.
c
START
8251AC
internal
reset
8251AC
mode
instruction
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