Data Access; Access Levels; Minimum And Maximum Values; Modbus Data Table - ABB RS485 Installation And Startup Manual

6 Data access

6.1 Access levels

Some access levels must be set to allow parameters to be changed. Here are some
access levels used in the RVT.
SET MODE: The RVT must be in the Set Mode to allow parameter modifications.
LOCKING SWITCH: the locking switch has to be released
BANK SETTINGS: the parameter bank settings must be set as Unlocked (for more
information on these settings, please refer to the RVT Installation and Operating manual).
Another parameter (COMMUNICATION LOCK) is used to add access rights to Modbus
users.
The access levels of the Modbus writings are coded in the Modbus data table.

6.2 Minimum and maximum values

Variables have a limited range. If a write operation to a variable exceeds the minimum
and maximum allowable values, the variable will be overridden with its minimum or
maximum value.
An ILLEGAL DATA VALUE exception error is sent back.
See the Modbus data table for more details.

6.3 Modbus Data table

Data are arranged in several tables for convenience. Individual tables contain similar
information. Table data may be read only or read/write access.
Data in each table is pointed to in a Modbus command by two consecutive data address
bytes. The first byte defines the table number, and the second byte the offset of the data
in the table. These two bytes are what is called the 'Modbus address' or the 'Modbus
register'.
A specific Modbus data table is dedicated to a specific product type.
Access (read or write) to a non-referenced Modbus address result in an ILLEGAL DATA
ADDRESS exception error.
The Modbus Data table gives all information on the various data and how to access them.
To handle RVT data, please refer to the RVT Modbus Data table.
16 – Data access  RS-485