Heathkit H9 - GENERAL INTERFACING; I;O CIRCUIT BOARD PROGRAMMING; EIA RS-232 C Serial Input;Output

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GENERAT
INTERFACING
I/O
CIRCUIT
BOARD PROGRAMMING
The I/O
circuit board
can
be
programmed (wired)
to
operate
in
one of three
serial input/output modes:
O
EIA RS-232C
o
TTL
o
TTY
(20
mA
current
loop)
You
can also
select one of five baud
rates
(600
to
9600), select the word length
(5-,6-,
7-,
or 8-bit), as
well as
generate
a
parity
bit
(odd
or
even).
The Video Terminal
is
wired
initially so that
it is
compatible with the
Heathkit H8 Digital Computer
System.
The various serial input and
output levels
and configurations
are
explained
in the following
paragraphs.
This information
will help
you interface
the Terminal with
your particular
system,
Always remove
the IiO circuit
board from
the Termi-
nal
before
you
make any
wiring
fprogramming)
changes.
EIA RS-232C
Serial
Input/Output
The Terminal is
initially wired for an EIA serial in-
put/output.
Pictorial
2-4
shows the
jumper
wires
necessary for this
configuration. The EIA input levels
are
shown in Pictorial 2-5. A
space
is
defined as a
positive
voltage between +3
and
+25 volts.
A
mark is
defined as a negative voltage between
-3
and
-25
volts.
Pictorial z-0
shows the
partial
schematic of the
EIA wiring
on
the I/O circuit board.
The
jumper
wire
that disables
the reader
control is
shown in
Pictorials
2-4
and 2-6.
Refer to "Reader
Control"
on Page
18.
ru
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sP
ACE
7,%,
RTADER
CONTROL
DISABLE
l/0
ctRCUlT
BOARD
PICTORIAL
2.4
PICTORIAL
2.5