Modbus Communication Interface | A-5
HOLDING REGISTERS
Since the RAM space on the analyzers is limited and not every customer’s DCS\SCADA\DAS\
PLC supports Modbus loating point value transfer, loating point values that are commonly
accessed on a Model 3050 analyzer are scaled and converted into integer values to load into
Modbus registers for transmission. The register values need to be scaled back at the receiv-
ing end to yield the actual values. The size of a Modbus holding register is 16-bit which can
assume a value from -32768 to +32767 in two’s complement. The holding register deini-
tions, units of measurement and scaling factors are shown in the following table.
Table A-1 Continued
Register #0 holds the moisture concentration value not held during veriication. This value
is in ppm.
A pair of registers #135 and #136 provide the same moisture concentration value in loating
point Modicon standard.
Register #1 holds the moisture concentration value held during veriication cycle. The units
of measurement are changing depending of lag status located in register #65.
A pair of registers #137 and #138 provide the same information in loating point format.
Register #11 is a DataState register, which is designed to synchronise the data acquisition
process. This lag is cleared by read. A value of one indicates new data is available.
Register #8 is the SystemState variable, which is set to alarms and warnings. This value is
decoded according to the table below.
Example: The value of SystemState is 12612 which is the same as 3144 hexadecimal num-
ber. Corresponding alarms started from the list signiicant bit are: Invalid Reading, Calibra-
tion Failure, Flow Alarm, Moisture Generator Date and Dryer Alarm.
Register #25 is a ModbusCommand register. This register allows sending special commands
to the 3050 analyzer as shown in the table below.
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