Motor Controllers AC Variable Frequency Drives
RVBS
Specifications are subjected to change without notice.10/08/2021
10
To make a clear distinction between Modbus RTU function codes and the RVBS
’s function codes, the former
will be hereinafter referred to as ‘FC’.
The ModBus exceptions supported are:
Subcode
Item
Description
Order of
priority
1
Improper 'FC'
The inverter received an unsupported FC. (See table
3.1.)
1
2
Improper
address
Improper
function code
An unused function code or a function code out of range
was received.
When the read/write data (except the first one) containing
an unused function code.
- During function reading
Zero (0) will be read, which will not result in an error.
- During continuous function writing
The writing will be ignored, which will not result in an
error.
2
Improper
number of
data
- When the number of read/write data is not between 1
and 10.
- No error will result when the value of the function code
plus the number of data is beyond the setting range of
the function code.
Diagnostic
code error
(maintenance
code)
A value other than 0 was received although the sub-
function code as the diagnostics was fixed to 0.
3
Improper
data
Data range
error
The write data is beyond the permissible write range.
3*1
7
NAK
No right of
writing
No right of writing by H28
Write disable
- Writing was attempted to the functions to which writing
from RTU is prohibited or to which writing is disabled
during operation.
*1 The priority between sub code 3 and 7 depending on a cause of sub code 7.
4.1.4
ModBus communication error
Communication errors number and type, when detected, are monitored to indicate the trend of the
communication. These errors are not memorized in the alarms log. In the following status variables are stored
the last error type and errors counter. The list below shows the communication error including logical error,
transmission error, and communications disconnection error.
Error category
Error name
Description
Error code
Logical error
Improper 'FC'
See "Table 2.d" shown in 2.1.3.
1(01H)
Improper address
2(02H)
Improper data
3(03H)
NAK
7(07H)
