132
ICC
Big Endian
Enable
Big Endian
if the transmitted values are to be encoded in big-endian, 16-
bit word order, i.e. the most significant 16-bit word is before the least significant
16-bit word.
Word-Size Register
Enable
Word-Size Register
if each target register is 16-bits wide, but two 16-bit
registers are to comprise one 32-bit value. If not enabled, each of the target
registers is assumed to be 32-bits wide.
Note that when
Word-Size Register
is enabled, the
Num Regs
field name
changes to
Num Reg Pairs
, indicating the number of pairs of 16-bit wide
registers to be addressed. When enabled, each register pair will use two register
addresses and the selected
Data Type
will be applicable for the register pair, not
the individual registers. For example, if the
Start Reg
is 100,
Num Reg Pairs
is
2, and
Data Type
is 32-bit Unsigned, then register numbers 100 – 103 will be
remapped, with registers 100 and 101 representing the first 32-bit Unsigned
value and registers 102 and 103 representing the next 32-bit Unsigned value in
the gateway’s database.
Word Count
Enable
Word Count
to interpret the Modbus “quantity of registers” field as the
number of 16-bit words to be transferred. If not enabled, the “quantity of
registers” field will be interpreted as the number of 32-bit registers to be
transferred.
Data Type
This field specifies how many bytes are used to store data for each register (or
register pair), as well as whether the internal value should be treated as signed or
unsigned when converted to a floating point number for transmission over the
network. Select the desired data type from this dropdown menu.
Note that each data type has different range limitations: 16-bit data types can
represent values up to 65,535, and 32-bit data types can represent values up to
4,294,967,295.
8.8.12.3
Configuration Example
This example will configure the gateway for end-to-end communication using
Modbus RTU Slave and EtherNet/IP Server.
Say, for instance, we wish to share data between two PLC’s. One PLC only
supports Modbus, while the other only supports EtherNet/IP. Since the PLC that
supports Modbus is already the lone master for the Modbus network, we cannot
set the gateway as a Modbus Master. Therefore the gateway must be set as a
Modbus Slave on the RS-485 port. Let’s assume that the Modbus PLC
exchanges information from different floors of a building. There are 3 floors. Floor
1 has 3 registers at address 1000, 1001, and 1002 for monitoring the floor status
