A-4 | 3050-SLR Moisture Analyzer
MODBUS FUNCTIONS
As the Modbus protocol is designed for communication among Programmable Logic Con-
trollers (PLCs), not all Modbus function codes supported by a slave PLC are applicable to the
Model 3050 analyzer. Only the following relevant function codes are implemented:
In accordance with MODBUS protocol speciications, all address references in Modbus mes-
sages are numbered relative to zero. For example, the irst holding register in a Modbus
slave being referenced as 40001 would be addressed as 0.
EXCEPTION CODE
The Model 3050 analyzer Modbus protocol implementation supports these exception codes:
Unsupported function requests from the Modbus master result in exception code 01 being
returned. Illegal address exception code is returned when the requested address is outside
the allowed range or writing to a read-only location. When the values to be written to hold-
ing registers are outside the appropriate ranges, exception code 03 is returned.
Figure A-3.
Modbus Function Code.
Figure A-4.
Exception Code.
CODE DESCRIPTION
03 Read multiple holding registers (4x references)
06 Write one holding register (4x references)
16 Write multiple holding registers (4x references)
17 Read slave ID and status information
CODE DESCRIPTION
01 Illegal Function
02 Illegal Address
03 Illegal Value
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