Watlow RMA PLUS RMAP-2A Series, User Manual

Page: 51 / 75

Version 1.0 PN: 2042-8198
Page 51 of 75 DN: 10-32813
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6: Write Single Register
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16: Write Multiple Registers
As a Modbus® RTU master, the RMA PLUS only implements the following Modbus® function codes:
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3: Read Holding Registers
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6: Write Single Register – Only if key RtuFc6 is enabled!
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16: Write Multiple Registers
Modbus® RTU supports all integer data types, floats, enums and Watbus Parameter types. Strings are
not implemented. See
Data Types for more information.
The 16-bit word / register order of multi-register data types may be changed to suit the client
application. By default, the word order is low, high. See
Modbus for member documentation.
The object model for the Modbus® RTU slave is user-defined. A sample file (shown below) exists in the
path defined by the keys
ModbusRtu6 and ModbusRtu7 . Add records to these files as necessary
keeping the following in mind:
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The Modbus® register is user-defined. It is an unsigned 16-bit integer with a range of 0 – 65535.
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Records must be sorted in ascending order by Modbus® register (Column A).
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The file may contain a maximum of 2000 valid records.
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There is currently a maximum of 500 unique data points per Watbus bus and zone.
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You must respect the data type of the target element i.e. 32-bit integers, floats and parameters
consume two registers, so you must skip a register number before starting the next custom data
point. In this example, additional records may be added starting at registers 2 and 1002 because
both elements are 32-bit values.
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A value of 0 will be returned for registers that are not explicitly defined in the table.
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An exception will be returned if a request exceeds the limits of the table, i.e. register > 1001 in this
example.
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Writing will not return an exception unless the above condition is violated.
Register Bus Segment Zone Class Instance Member Refresh Count
0 1 0 0 1 1 1 0 DEV 1 Hardware ID
1000 1 0 0 36 1 19 0 RTC 1 Timestamp
Figure 47 - ModbusRtuX.csv default configuration
Perform test read / write operations on the data. A sample Modbus® RTU test program is included on
the MICRO SD drive for testing purposes (sd:\Software\Modbus RTU). In the following example, the
RMA PLUS’s Hardware ID (32-bit Integer) is returned for registers 0, 1. Registers 2 and 3 were not
specified so they return 0s.