B.1
APPENDIX B MODBUS PROFILE
The analyser supports Modbus slave communication through the serial data connector (PL6).
This supports an RS232 or RS485 multidrop link to a Modbus master. The implementation of
Modbus is based on the “Modicon Modbus Protocol Reference Guide PI-MBUS-300 Rev. J”
dated June 1996.
The following facilities are provided:
• Access to measurement data
• Access to derived measurement data
• Access to external analogue input data
• Access to measurement status and alarm information
• Access to analyser status information
• Initiation of individual autocalibration groups
• Progress indication of autocalibration
• Ability to stop current autocalibrations
• Diagnostic and error functions
These are described below.
Measurement data
Measurement data from each of the four possible transducer positions is available in a block
of input registers that can be read using Modbus function code 04.
NOTE
Measurement data is in IEEE 754 floating point format. Each value requires 2 registers as
follows:
Register N = High word
Register N + 1 = Low word
Registers Name Comments
30001 – 30002 I1 Measurement Measurement 1 value in IEEE 754 floating point format
30003 – 30005 I1 Name A 6 character string containing the measurement 1 name
30006 – 30007 I1 Units A 3 character string containing the measurement 1 units
30008 – 30009 I2 Measurement Measurement 2 value in IEEE 754 floating point format
30010 – 30012 I2 Name A 6 character string containing the measurement 2 name
30013 – 30014 I2 Units A 3 character string containing the measurement 2 units
30015 – 30016 I3 Measurement Measurement 3 value in IEEE 754 floating point format
30017 – 30019 I3 Name A 6 character string containing the measurement 3 name
30020 – 30021 I3 Units A 3 character string containing the measurement 3 units
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