~
7
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NOVATEK-ELECTRO
ЕТ-485
WARNING! CONTINUOUS ACTIVATION OR FLASHING OF “ERROR” INDICATOR IN THE ABSENCE
OF CONNECTIONS TO THE UNIT INDICATES UNIT MALFUNCTION.
Etherne
t network connection pending. The network connection is established, if “
Ethernet
” indicator
becomes activated. Flashing of “
Ethernet
” indicator stands for transmitting data over the network.
Figure 4
– Unit connection diagram
6.2. OPERATING
ЕТ-485 OVER THE HTTP PROTOCOL
ET-485 waits for a connection to an Ethernet network using the HTTP protocol on port 80. PC connection can
be established using the WEB-browser.
When a client connects to port 80, the unit starts expecting requests for HTML-pages. These requests may
contain certain parameters. In case of a valid request, those parameters are processed and the client receives the
text of a selected HTML-page. In case of a request without an indication of certain page, the client is returned to the
title page. When the page is transferred, the unit deactivates the client and awaits for further connection.
6.3. OPERATING
ЕТ-485 OVER THE MODBUS TCP PROTOCOL
While operating, the ET-485 waits for a connection to an Ethernet network using the Modbus TCP protocol
on port 502. The connection port for Modbus TCP can be changed by the user. PC connection can be established
using any software
– Modbus TCP of the clients. Client software for ОС Windows can be downloaded from the
manufacturer's web-site (http://novatek-electro.com/programmnoe_obespechenie.html).
When a request for client connection to the Modbus TCP port is received, the unit starts verifying the client's IP-
address (if connection filtering over IP is activated). If this address does not correspond with the preset value, the
connection is rejected. Otherwise, the unit starts checking the list of available connections. In case of no available
connections, the unit (depending on the configuration) can connect a new client instead of the previously connected
one (if no activity of the client was registered over a set period of time, or if the connection is maintained longer than
prescribed).
When connecting a client to Modbus TCP port, the unit adds it to the internal list of served clients (but not
exceeding the number of clients, specified in the technical characteristics).
When connection of the client is established, the unit awaits a Modbus-query from the client. In the RS-485 slave
mode, the device also accepts RS-485 queries from the master device of Modbus network.
When the query from the client has been received, the unit analyzes the query and, depending on the
requested function code and the current rights of the client, either processes or blocks it. When the query is
blocked, ET-485 can generate and transfer the client-specified Modbus exception code (default
– code 1) to the
client. The rights of the client, depending on the settings, are determined according to its IP address (the Modbus
network master IP address is considered to be 127.0.0.1) and input passwords.
If the query is addressed to
ЕТ-485, the unit does not redirect the query, processes it and transfers the answer
to the client.
In the RS-485 master mode, queries to other devices are redirected to Modbus network and an answer form
Modbus network is awaited
– herewith the
«RS-485»
indicator will start to glow. If the data have been received or
the standby time has run out, the
«RS-485»
indicator will go out.
