SATEC ETC2002 - Manual (Page 17)

Chapter 3 Operating the ETC2002 Using the ETC2002
ETC2002 Network Communicator 17
ETC2002 Network Applications
Transparent Gateway
The ETC2002 normally provides a means for transparent exchange of
messages between master Internet and serial client applications, and slave
serial or wireless devices.
The ETC2002 can manage up to eight concurrent sessions between master
stations and slave devices. Each connection is fully transparent for the
master. The ETC2002 forwards client requests to target devices, and then
returns responses to the master application, maintaining all timing
regulations required by the protocol. The serial networks are accessed in a
queued manner that prevents possible collisions.
Data Server
The ETC2002 has an embedded Data server that allows the user to save
time required for polling multiple devices, especially via slow serial
interfaces. It utilizes the ETC2002 non-volatile memory for automatic data
acquisition.
The Data server is accessible via the Modbus/TCP protocol from any remote
application. The user application can read blocks of ready data directly from
the ETC2002 memory exchanges without the need to wait until slow devices
respond to master requests.
The Data server can also perform a delayed write of data so the application
does not need to wait until the device is accessible, but rather can write data
to the ETC2002 memory exchanges, with the ETC2002 then taking
responsibility for delivering data to the target devices.
The Data server can also periodically poll device status registers, record
events to a log file and give alerts on specific events.
The following table gives a summary of the available data exchanges.
Exchange Type Number of
Exchanges Exchange Block
Size, registers
Real-time data exchange 250 1-114
Status event exchange 250 1
Data write exchange 250 1-12
NOTE:
The real-time, status event and write data exchanges with the
same exchange number are internally linked in the ETC2002 to
the same device address. If you change the device address for
one of the exchanges, the same address will be taken for other
configured exchanges that have the same exchange number.
See Configuring Data Server in Chapter 5 for information on configuring data
exchanges. Refer to the ETC2002 Modbus Guide for information on
accessing and retrieving data from the Data server exchanges.
Real-Time Data Exchanges
Real-time data exchanges are used for periodic retrieval of data from the
connected devices. The ETC2002 provides up to 250 real-time data
exchanges of 1 to 114 registers long. They are directly accessible from
remote master applications.
When the Data server is enabled, it acquires data from the connected
devices either continuously, or on a periodic basis. If continuous polling is
disabled, the devices are requested periodically at predefined poll intervals.
If continuous polling is enabled, the ETC2002 retrieves data from the devices
in turn without pauses.
You can individually enable or disable polling data for a specific exchange. If
the device has an onboard real-time clock, you can enable periodic RTC