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4 FUNCTION CODE NUMBERING AND BEHAVIOR
4.1
Register Numbers
All accessible inverter function codes can be referenced by their Modbus register indices, as defined in
the
RS-485 User’s Manual (24A7-E-0082)
, section 3 (Table 3.2) and can be conveniently referenced in
the configuration studio (section 5.6) and the embedded web server (section 6.2.3). These same register
numbers are used when accessing function codes via certain Ethernet protocols. The terms “function
code” and “register” refer to data stored on the inverter and will be used interchangeably throughout this
documentation. The max supported register number is 13668. Because the RS-485 User’s Manual
contains information for several Fuji inverter families, the relevant information will be paraphrased here
for the specific case of the FRENIC-Ace.
All inverter function codes are exposed as register indices according to a mathematical conversion
formula which combines two elements (a function code group number and function code offset) to create
a unique register number for each function code. Each function code group (“E” / Extension Terminal
Functions, for example) is assigned a specific function code group number (refer to Table 14). Each
function code also has an offset number, which is the function code without the leading letter (the offset
number for function code E05, for example, is 5). To determine the register number for a given function
code, therefore, the group number is first multiplied by 256, then added to the offset number plus 1. This
operation is expressed mathematically via Equation 1.
(
)
1
number
offset
256
x
number
group
register
+
+
=
Equation 1
As an example, let’s calculate the register number for output frequency (function code M09). According
to Table 14, the group number for the “M” function code group is 8. It is also evident that the offset
number for M09 is 9. Inserting the group number and offset number into Equation 1, we arrive at the
result indicated in Equation 2.
(
)
2058
1
9
256
x
8
=
+
+
Equation 2
While manually calculating all of the register numbers for the function codes 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).
Note that not all of the available registers that exist in the interface card’s register map have
corresponding function codes 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 function code 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 function codes and some of which do not), while only manipulating those in your local
programming that are known to exist.
