ABB CSU-2LV, Installation And Maintenance Manual, Page: 43 / 84

ABB
ARC GUARD SYSTEM™ – CSU-2LV/2MV INSTALLATION AND MAINTENANCE GUIDE 43
6.6 Functional description
The information found here is the basic information
needed for the installation of CSU-2 in a Modbus system.
6.6.1 Implementation class
The physical and data link layers are implemented
conforming to the “basic slave” implementation class
as described in document [2] “MODBUS over Serial Line
specification and implementation guide V1.02”. The
following options have been implemented:
Table 5 Modbus Parameters
General settings
Parameter
Options Remarks
Addressing address configurable 1-248 (default 248) When set to 248, the communication is
disabled.
Baud rate 9600
19200 (default)
38400
57600
Selectable frame formats 8 bits, even parity, 1 stop bit (default)
8 bits, odd parity, 1 stop bit
8 bits, no parity, 1 stop bit
8 bits, no parity, 2 stop bits
Electrical interface RS485 2W cabling
6.6.2 Supported Modbus functions
This section describes the supported Modbus function
codes.
6.6.2.1
Read Registers (03, 04)
Both function 03, Read Holding Registers and function 04,
Read Input Registers, can be used. The addresses are the
same.
Table 6 Read Exceptions
Possible exception responses
Code
Name Meaning
02 ILLEGAL_DATA_ADDRESS Address refers to a register that is not available
or not readable.
6.6.2.2
Write Registers (16)
Function 16, Write Multiple Registers, are supported.
Table 7 Write Exceptions
Possible exception responses
Code
Name Meaning
02 ILLEGAL_DATA_ADDRESS Address refers to a register that is not available
or not readable.
03 ILLEGAL_DATA_VALUE The value written is not permitted for this
register.
06