FRICK
®
QUANTUM™ COMPRESSOR CONTROL PANEL S90-010 CS (APR 08)
COMMUNICATIONS SETUP Page 37
MODBUS NOTES:
This has been an example of how the Quantum™
Controller uses the Modbus Protocol. It is hoped that the
information provided here will assist the end user in writing
applications that will allow the Quantum™ to be
implemented into networks that the customer may already
have in use.
This information is subject to change at any time, and is
provided as a reference only. Not all areas of the Modbus
Protocol can be handled in this document. Some
additional information regarding Modbus Protocol that the
end user should be aware of:
•
There are many versions of Modbus Protocol that
is available, and an application that works
properly on one system, may not function
identically on another.
•
Some versions of Modbus Protocol may require
the user to increment any referenced addresses
by 1 (one). For instance, if you wanted to look at
Frick
®
Address 135, you may need to actually
look at address 136. The Quantum™ addressing
begins at 0 (zero), whereas some Modbus
Protocols begin at 1 (one), therefore, you may
need to compensate.
•
DO use Modbus ASCII. DO NOT use Modbus
RTU.
•
7 or 8 Data bits may be used.
•
1 or 2 Stop bits may be used.
•
Parity can be set to
None
,
Odd
or
Even
•
Follow the Frick
®
specifications for data
communications requirements.
NOTE: Be careful not to continuously request a
setpoint change. It is to be expected that
communications may slow down during the process
of writing setpoints or clearing alarms. Both of these
processes involve writing to either EEPROM or Flash
Memory and does take some time. If communication
requests are being sent faster than once every couple
of seconds, there will be temporary slowdowns during
these processes.
