Modbus Configuration; Figure 35 - Expansion I/O - Elpro Technologies 915U-2 User Manual

915U-2 Wireless I/O Page 59
By default the Data Rate, Data Format will
all be standard 9600, N81 and none for Flow
Control which matches the default Serial
baud rate and data Format of the 115S
serial expansion module.
Serial parameters can be adjusted for
compatibility or faster serial performance by
adjusting the rates and format and then
selecting the "Save and Activate" Button.
Serial port parameters will also need to be
changed on the expansion I/O module by
using the 115S Configuration Utility which
can be downloaded from the ELPRO
Technologies Website (www.elprotech.com)

Figure 35 - Expansion I/O

Maximum Number of Expansion Modules to Poll – This is the maximum number of
slave addresses that the Modbus Client will scan or poll for. Default is 3. If adding more
that 3 115S expansion I/O module this number will need to be increased.
Maximum Number of Connections – Enter the maximum number of simultaneous
TCP connections to the server allowed.
Request Pause – Enter the delay between serial requests in milliseconds
Response Wait – Enter the serial response timeout in milliseconds – a serial retry will
be sent if a response is not received within this timeout.
Maximum Tries – Enter the maximum number of request retries performed serially.

4.2.10 Modbus Configuration

The 915U-2 provides Modbus TCP Client and Modbus TCP Server functionality for I/O
transfer. There are pre-defined areas representing Inputs and Outputs as well as the
different I/O types, e.g. Bits, Words, Long, Floats, etc, which include the onboard
Input/Output) and are shared for both Client and Server. For a full list of the available
I/O and address, locations please see 915U-2 User Manual.
Modbus TCP Client (Master) and Modbus TCP Server (Slave) are both supported
simultaneously, and when combined with the built in Modbus TCP to RTU Gateway the
915U-2 can transfer I/O to/from almost any combination of Modbus TCP or RTU
devices.
Modbus TCP Server (Modbus Slave) enables the 915U-2 to accept connections from
one or more Modbus TCP Clients (Masters). All Modbus transactions routed to the
onboard Modbus TCP Server are directed either to/from the onboard general purpose
I/O registers. The Modbus TCP Server is shared with the Modbus TCP to RTU
Gateway, so that the Modbus "Device ID" is used to determine if a Modbus transaction
is to be routed to the onboard Modbus TCP Server or to a Modbus RTU device
connected to the serial port. Care should therefore be taken that all serially connected
Modbus devices use a different Modbus Device ID (i.e. Modbus Slave Address) to the
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