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NC Serial
Appendix
Communications Protocol
NOTE This appendix assumes you have a basic understanding of
communications protocols.
All data is sent and received in binary form, do not use ASCII. In the
following pages the binary data is represented in hexadecimal (hex) format.
The NC Serial Communications Protocol is based on a master-slave
model. The master is a host computer, while the slave is the chiller's
controller. Only the master can initiate a communications transaction
(half-duplex). The slave ends the transaction by responding to the master's
query. The protocol uses an RS-232 serial interface with the default
parameters: 9600 baud, 8 data bits, 1 stop bit, no parity and no
handshaking.
NOTE Before the chiller will communicate, RS-232 must be turned on
using the controller. Ensure the
indicator is illuminated.
The chiller can be controlled through your computer's serial port by using
the chiller's standard 9-pin RS-232 connection. Data read of the serial
port connects to the data transmit (pin 2) of the chiller. Data transmit of
the serial port connects to data read (pin 3) of the chiller.
Communication cables are available from Thermo Fisher. Contact our
sales department for additional information.
All commands must be entered in the exact format shown in the tables on
the following pages. The tables show all commands available, their format
and responses. Controller responses are either the requested data or an
error message. The controller response must be received before the host
sends the next command.
The host sends a command embedded in a single communications packet,
then waits for the controller's response. If the command is not understood
or the checksums do not agree, the controller responds with an error
command. Otherwise, the controller responds with the requested data. If
the controller fails to respond within 1 second, the host should resend the
command.
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