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4–2
Input and output levels on the RS-232 port conform to the RS-232-C
standard. The transmitter has increased capability to drive an isolated line
that is up to 7,000 feet long. The length of this line determines the
maximum communication rate on the RS-232-C link:
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;<)&")0=>>>
5?=0>>
0=>>>)&")@=>>>
?=A>>
@=>>>)&")A=>>>
@=7>>
A=>>>)&")6=>>>
0=@>>
The receiver can sense the signals generated by a similar transmitter, and it
is electrically isolated from all other circuitry on the module. It consists of
an opto-isolater circuit with an input and return line at the RS-232-C port.
All other signals on the RS-232-C port are driven and received by standard
RS-232-C interface circuits, which have maximum drive capability of 50
feet.
The 1785-KE module sends data serially over the RS-232-C interface, one
8-bit byte at a time. The transmission format conforms to ANSI X3.16,
CCITT V.4, and ISO 1177, with the exception that the parity bit is retained
while the data length is extended to eight bits.
The transmission format may be summarized as:
start bit
data bit 0
data bit 1
data bit 2
data bit 3
data bit 4
data bit 5
data bit 6
data bit 7
even parity bit (optional)
one stop bit
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