Thermo Scientific ULT-80 Installation & Operation Manual page 55

Appendix A Serial Communications Protocol
NOTE: This appendix assumes you have a basic understanding of communi-
cations 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 bath'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, 1 start bit,
8 data bits, 1 stop bit and no parity.
NOTE: Before the circulator will communicate, RS-232 must be turned on in
the controller's Setup Loop.
The circulator can be controlled through your computer's serial port by using a
standard 9-pin RS-232 connection on the rear of the temperature controller.
Data transmit of the computer's serial port connects to data read (pin 3) of
the bath. Data read of the computer's serial port connects to the data transmit
(pin 2) of the bath.
Communication cables are available. Contact our sales department for
additional information.
All commands must be entered in the exact format shown in the tables on the
following pages. Table 1 shows 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 sending 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 re-send the command.
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