8
3 Data Server
3.1 Data Server Features
The Data server allows the user to save the time required for polling multiple devices, especially via
slow serial interfaces, by utilizing the ETC2002 non-volatile memory for automatic acquiring data. The
user application can then read blocks of ready data directly from the ETC2002 memory 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 needs not to wait until the device would be accessible, but rather can
write data to the ETC2002 memory exchanges, and then the ETC2002 takes responsibility for
delivering data to the target devices. The Data server can also periodically poll device status registers
and record events to a log file or give alerts on specific events.
The following table lists the configurable Data server options.
Table 3-1 Data Server Options
Description Range
Data server enabled
1=enabled, 0=disabled
Continuous polling
1=enabled, 0=disabled
Data polling interval
1-1000 min
Data logging interval, polls
0-1000, 0=logging disabled
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.
Acquired real-time data is normally stored in the ETC2002 exchanges (memory blocks) and is
periodically refreshed at programmed intervals. The ETC2002 provides up to 250 real-time data
exchanges of 1 to 114 registers long. These exchanges can be directly accessed by the master
application.
If the user wishes, acquired data can be periodically moved to historical circular files where it will be
kept for a long time until it is overwritten by newer data. Data is stored to historical files at regular
intervals. The logging interval is always represented as a whole number of data polling intervals even if
the polling itself is not synchronized with polling intervals like in the event of continuous polling. Since
the ETC2002 tries to synchronize polling devices with the beginning of an hour, it is recommended to
program a logging interval in such a manner that it would be a whole divisor of 60 minutes. Historical
records can be accessed one record at a time either in an arbitrary order, or in a sequential manner.
The ETC2002 also provides up to 250 write data exchanges, of 1 to 12 registers long, and up to 250
status event data exchanges of 1 register long. Table 3-2 gives a summary of the available data
exchanges.
Table 3-2 Data Server 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 ID. If you change the device ID for one of the
exchanges, the same ID will be taken for other configured exchanges that have the same exchange
number.
