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4 PARAMETER NUMBERING AND BEHAVIOR
4.1
Register Numbers
All accessible inverter parameters can be referenced by their Modbus register indices, as defined in the
A1 Instruction Manual
and can be conveniently referenced in the studio (section 5.6) and the
embedded web server (section 6.2.3). These same register numbers are used when accessing
parameters via certain Ethernet protocols. The terms “parameter” and “register” refer to data stored on
the inverter and will be used interchangeably throughout this documentation. The relevant information
will be paraphrased here for the specific case of the A1.
All inverter parameters are exposed as register numbers according to a mathematical conversion
formula which combines two elements (a parameter group number and parameter index) to create a
unique register number for each parameter. The parameter groups are listed in Table 13. Each
parameter also has an index, which is the parameter without the leading group number (the index for
parameter 01.02, for example, is 2). To determine the register number for a given parameter, therefore,
the group number is first multiplied by 256, then added to the index plus 1. This operation is expressed
mathematically via Equation 1.
(
)
1
index
256
number x
group
register
+
+
=
Equation 1
As an example, let’s calculate the register number for deceleration time1 (parameter 23.05). The group
number is 23 and the index is 5. Inserting the group number and index into Equation 1, we arrive at the
result indicated in Equation 2.
(
)
5894
1
5
256
x
23
=
+
+
Equation 2
While manually calculating all of the register numbers for the parameters of interest is certainly possible
by using Equation 1, it may be more convenient to simply reference the “Register” column on the
monitor tab of the default web interface (refer to section 6.2.3). The parameter to register mapping list is
also available in the studio.
Note that not all of the available registers that exist in the interface card’s register map have
corresponding parameters that exist in the inverter. In other words, if a read from or write to a register
number that does not correspond to an existing inverter parameter takes place, the read/write may be
successful (depending on the specific register accessed; refer to section 4.2), but the data will have no
meaning. This feature is beneficial in situations where the accessing of non-contiguous registers can be
made more efficient by accessing an all-inclusive block of registers (some of which correspond to
inverter parameters and some of which do not), while only manipulating those in your local programming
that are known to exist.