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inverter. If the value was not accepted by the inverter, then the unsuccessful write can be observed by
reading the current (unchanged) value of the register during a subsequent network transaction. If the
unsuccessful write was initiated via the web browser’s monitor tab, then the displayed register will revert
back to its original value automatically.
Accesses to any register in the scanned register range (1794..1807, 2050..2122, or 3842..3937) will
always be successful. Even if an inverter function code corresponding to a given scanned register does
not exist, the interface card still maintains a location in its internal mirroring memory for that register.
This feature allows for the block access of non-contiguous registers as described in section 6.1.
The second class of registers is called “
non-scanned registers
”, and is comprised of all inverter
configuration function codes and alarm-related function codes. Non-scanned registers are not
continuously accessed by the interface card. What this means is that for those protocols that allow
accesses to non-scanned registers, such accesses will incur additional response latency, as the
interface card must first forward the request to the inverter for it to process.
While the principle disadvantage of accessing non-scanned registers is the additional delay that is
incurred, the unique advantage that non-scanned register accesses provide is that write data checking is
available. Because all non-scanned register accesses must first be processed by the inverter itself,
issues such as out-of-range data values will always be checked for, and any applicable errors will be
immediately returned to the originating network protocol.
For those protocols (such as Modbus/TCP) that allow access to non-scanned registers, note that the
inverter applies the following rules to these accesses:
•
A maximum of 50 registers may be read or written in one transaction
•
If only one non-scanned register is accessed in a particular transaction, then that register must exist
in the inverter, or an error will be returned.
•
Reading registers: if more than one non-scanned register is accessed in a particular transaction,
then at least the starting register must exist in the inverter, or an error will be returned. Any non-
existent registers accessed as a result of the remainder of the request will be returned with dummy
“0” values.
•
Reading registers: registers cannot be read across function code groups. Any multiple-register
request will return dummy “0” values for all registers that extend past the last register in that group.
•
Writing registers: if more than one non-scanned register is targeted in a particular transaction, then
at least the starting register must exist in the inverter, or an error will be returned. Write data
corresponding to any non-existent registers targeted as a result of the remainder of the request will
be ignored.
•
Writing registers: registers cannot be written across function code groups. Write data
corresponding to any registers that extend past the last register in a group will be ignored.
