Communications Protocol; Vs. Rs-485; Parameters - Honeywell SC1000 Owner's Manual

7.3 Communications Protocol

7.3.1 RS-232 vs. RS-485

7.3.2 Parameters

page 48 008-0608-00
SC Series instruments are available with either of two communications protocols, RS-
232 or RS-485. Only one of these can be installed at a time at the factory.
• RS-232 provides for only one receiver and transmitter per loop, and a loop length
of no more than 50 feet.
• RS-485 allows up to 32 devices per loop, and a loop length of no more than 4000
feet. All devices receive messages in parallel on the line, the so-called "multi-
drop" system. To avoid garbled transmissions, only one device should respond to
a particular message. Therefore, every device on the loop must have a unique
address.
If you have an instrument with more than one channel, transmission must be
addressed to the appropriate channel within the instrument.
All SC instruments use no parity, 8 data bits, and 1 stop bits ("N,8,1") for serial com-
munications. Baud rates available are 300, 600, 1200, 2400, 4800, 9600, 19200
and 38400. As shipped from the factory, all instruments are set at 9600 baud. The
baud rate can be selected though the front panel.