Xylem System 5000 User Manual - Manual (Page 91)

Modbus
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Register addresses begin numbering at 1. Some Modbus Masters and Slaves, however,
retrieve registers starting at address zero. An offset of one should be used in those cases. For
example, to retrieve the value at address zero of a PLC acting as a Modbus Slave, a Modbus
Master Input could be used by setting the register address to one.
Defines which Modbus table the selected register is a part of. Only corresponding function
codes can retrieve registers from the selected table. Typically Holding Registers or Input
Registers are used for reading and writing values in Modbus. Multiple registers can be
assigned with these tables by changing the Number Type. Discrete Input and Coil can only
contain a 1 or 0 value and are generally associated with either a digital port or a true/false
condition.
Table
Determines the type and range of a given number. The Short number type is the default
Modbus type, using 1 Modbus register. Due to its limited range, the Long and Float types
are also available to store larger and more complex numbers and use two registers. The two
registers may be swapped by selecting the Inverse option. Short and Long store only whole
integer values (non-decimal) and can be unsigned, allowing only positive values, to enable a
greater range. Float stores a floating-point number. Binary types are only available for Discrete
Input and Coil types.
Number Type
Depending on the Number Type chosen, the number range will update, indicating what values
are supported with the given number type.
Number Range