OpenPCS 7 interface
6
6.1
Access options
Access options
The following table lists the options for access to the PCS 7 OS server and the central archive
server via OPC:
Access to data
from
Access
via OPC
Data type
Type of access
OS server
DA
Tags in process mode
Reading / writing
OS server
HDA
Archive tags in the measured value archive
(TagLogging)
Read
OS server
A&E
Alarms and messages
Read/
acknowledge
OS server
"H" A&E
Alarms and messages from the message archive Read
Central archive
server
"H" A&E
Alarms and messages from the message archive Read
Central archive
server
HDA
Archive tags in the measured value archive
(TagLogging)
Read
6.2
Data transmission
Type of data transfer of OPC DA, OPC HDA and OPC A&E
This section explains the various types of data transfer.
Event-driven data transfer
With event-driven data transfer, the OPC registers the required data for updating on the OPC
server. The OPC server sends the tags to the OPC client when they change.
Asynchronous data transfer
When using asynchronous data transfer, the called method is not completely processed on
the OPC server before the OPC client receives data from the OPC server. The OPC server
returns the results of the asynchronous operations using events. In this way, it is possible for
the OPC server to supply data to the OPC client automatically if the data has changed.
OpenPCS 7
Function Manual, 05/2012, A5E02780178-02
45
