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SECTION 8 SERIAL COMMUNICATIONS
8-0 Outcard RS232/RS422 Serial/Strobe Interface
This section applies to units which have the
Serial Communications interface option. Up to 15
units can be linked together. Unit status can be
accessed and new set points and K Factors can be
entered through the serial port. The unit cannot
be taken out of the Run Mode through the serial
port. Menu changes must always be made
through the front keypad (except Preset A, Preset
B, and K Factors). Data is transmitted at
selected baud rates using standard seven bit
ASCII characters and parity with two additional
bits of "Start" and "Stop" to make up the standard
ten bit character.
8-1 Unit Code
Each Unit in the hookup must be assigned a code
number from 1 to 15, through the front keypad, in
the OUTCARD setup mode (see Section 3-3,
Menu Item 5). Number "00" is reserved for a
dedicated hookup to only one terminal and its
transmit output line remains in an "on" active
state. (Units assigned other numbers have
outputs that remain in the "off" high impedance
state until addressed by their code number or
brought on line by a positive edge of the Strobe
input). Once a unit is addressed, do not address
another unit until the data has been sent and any
data requested has been transmitted back.
8-2 Baud Rate
The Baud rate is the speed at which data is
transmitted, expressed in bits per second.
Baud rates of 300, 600, 1200, 2400, 4800, or 9600
are available. Use the front keypad to call up the
OUTCARD setup mode (see Section 3-3, Menu
Item 3) and select the desired baud rate that is
compatible with the remote terminal.
8-3 Parity
Parity is a bit of information that is inserted
before the stop bit and is used to help check
if the transmission is correct. In the
OUTCARD setup mode, select between:
a) ODD (Parity bit is logical zero if total
number of logical 1's in the first seven bits
is odd)
b) EVEN (Parity bit is logical zero if total
number of logical 1's in the first seven
data bits is even.)
c) MARK (Parity data bit is always logical 1.)
d) SPACE (Parity data bit is always logi
cal 0.).
The Unit does not check the parity but does
transmit the parity chosen.
Idea:
Use the MARK parity for terminals that need two
stop bits and/or no parity since these terminals
ignore the parity anyway.
Note: If the parity of the terminal is not known,
it is often practical to key in a different parity
until the correct one is found.
8-4 RS232 Electrical Requirements
The Unit uses standard EIA specifications.
Standard inputs must present a load of 3000 to
7000 ohms. A voltage level of +3 V to +25 V
(referenced to signal ground) is read as a "Space"
or "0" and indicates an active state (asserts a
control line). A voltage level of -3 V to -25 V
(referenced to signal ground) is read as a "Mark"
or "1" and does not indicate an active state (does
not assert a control line). Outputs must send a
voltage of +5 V to +25 V (referenced to signal
ground) for a "Space" and a voltage level of -5 to -
25 V for a "Mark" when loaded with a 3000 ohm
load to signal ground. Outputs must be capable
of being shorted to other signal lines without
burning out.
Note: It is normally recommended that cable
length be limited to 50 feet.
Summary of Contents for KEPtrol F/C
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