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Example of setting up Modbus Master Map module's Device Map setup register

Published date: 15 March 2019

The Modbus Master Map module provides a common location to hold the setup information needed for decoding a Modbus response.  One Modbus Master Map module holds information that can be used by several Modbus Master Device modules.  There are several setup registers that need to be setup properly.  Device Map setup register will be discussed in this article.

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ION meters

Modbus Mastering

Modbus Master Device modules are associated with a Modbus Master Map module (by specifying the same Device Type for both the Modbus Master Map and the Modbus Master Device modules).  As such it is imperative to setup Modbus Master Map module, otherwise, Modbus Master Device module will not function properly.

The Device Map string contains the label, Modbus address, format, register size and scaling information.  One line of an example string is shown below:


Each line contains commas and prefixes for each component (e.g. Label).  These commas and prefixes must always be included in each line, in the exact place as shown above.

Mapping information for up to 32 Modbus registers can be stored within Modbus Map setup registers. The registers have to be within any 125 Modbus register block.

Lets assume five registers from a ION6200 device will be imported: Vln a, Vln b, Vln c, kW tot, kWh del.  Note that it is necessary to refer to 6200 Modbus Map document to obtain Modbus addresses and formats for the required registers (this document is attached).

The constructed string using the above format will look like:
LbVln a,SR40100,FUINT16,NR1,S1,O0,
LbVln b,SR40101,FUINT16,NR1,S1,O0,
LbVln c,SR40102,FUINT16,NR1,S1,O0,
LbkW tot,SR40120,FSINT16,NR1,S1,O0,
LbkWh del,SR40138,FU32-2143,NR2,S1,O0,

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