136
ICC
8.8.13
Modbus RTU Sniffer
To configure the gateway for Modbus RTU Sniffer, click on the
RS-485
Configuration
tab and select
Modbus RTU Sniffer
in the protocol dropdown
menu. The Modbus RTU Sniffer driver is passive (listen only), and uses service
objects to define what registers to log values for from the network traffic. For
more information on service objects, refer to section 8.5. Each register (input or
holding) in a service object is mapped to 2 bytes in the database (the data type is
fixed at 16-bit). For more information on register mapping, refer to section
11.12.2.1.3.
8.8.13.1
Protocol Selection Group
Protocol
Select
Modbus RTU Sniffer
from this dropdown menu.
Baud Rate
Select the desired network baud rate from this dropdown menu.
Parity
Select the desired network parity and number of stop bits from this dropdown
menu.
8.8.13.2
Modbus Sniffer Service Object Configuration
This section describes the configurable fields for a Modbus sniffer service object.
For more information on Modbus service object editing options, refer to section
8.6.
Type
This group designates the Modbus register type that this service object will log
(capture data for). Choose from Holding Register or Input Register.
Description
This field is a description of the service object. It is not used on the gateway, but
serves as a reference for the user. Enter a string of up to 16 characters in length.
Dest Address
This field indicates the node address of the remote slave device on the network
that contains the register(s) to be logged by this service object. Enter a value
between 0 and 247. Note that address 0 is defined by Modbus as the broadcast
address: if this address is used, the
Read
function checkbox must be
unchecked, since slaves cannot respond to broadcast messages.
Note that using a destination address of 0 will configure the service object to only
log broadcast messages; however, if a destination address other than 0 is used,