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Cole Palmer
Appendix
NC Serial 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/RS-485 serial interface with the default
parameters: 9600 baud, 8 data bits, 1 stop bit, no parity and no
RS-232 handshaking. RS-485 offers a a slave address selection from 1 to
100, default parameter: 1.
The unit can be controlled through your computer’s serial port by using the
unit's standard 9-pin connection.
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.
