ControlByWeb XW-110, User Manual

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Modbus/TCP (XW-110-Plus only) XW-110™ WiFi Temperature Sensor Users Manual
Section 5: Modbus/TCP (XW-110- Plus only)
XW-110- Plus can be controlled and monitored using Modbus/TCP protocol. This provides a standard
means of using XW-110- Plus with devices and software from other manufacturers. This section is not a
tutorial on Modbus and it is assumed that the reader is already familiar with Modbus. Detailed Modbus
information can be found at http://www.modbus.org.
Note: Modbus communications are disabled whenever the Control Password is enabled. This is
because Modbus/TCP does not provide a mechanism for password protection. Make sure the Control
Password is disabled (default) and Modbus functionality is enabled on the WiFi Network
tab.
XW-110- Plus functions as a Modbus slave. Host devices, such as PLCs, open a connection with XW-
110- Plus on port 502 (configurable under WiFi Network tab) and then send requests to read sensor
values. The XW-110- Plus has no write registers. When XW-110 receives a command, it will perform the
desired function and return a response.
The following sections provide an overview and explanation of Modbus operation.
5.1 XW-110- Plus Modbus Function Code Summary
XW-110- Plus supports the following function codes:
Code Name Modbus
Function XW-110 Feature XW-110 Start Address
Hexadecimal Decimal
Read Battery Voltage 03 Battery Voltage 0x0010 16
Read Sensors 03 Sensors 1-3 0x0110-0x0114 272-276
Multiple commands may be sent without closing and re-opening the connection, but if no data is
transferred for 50 seconds, the connection will time out and close. To keep the connection open, a read
request can be sent periodically.
XW-110-
Plus has two TCP sockets available for Modbus/TCP. This allows two connections to be open
at one time. Requests for more than two open connections will be rejected.
When errors occur, an error code is returned. Most Modbus client software will interpret this code in a
human readable form. The code is comprised of the original function code plus 0x80. For example, an
error during the read coils function 0x01 would return 0x81. Each error has a qualifying exception
number. The following are the possible exception codes and their meanings:
0x01 - Function code not supported (also when Modbus is disabled in the setup pages).
0x02 - Incorrect starting address/quantity of output combination.
Page 38 Xytronix Research & Design, Inc.