The update rate will be set by the OPC
client, and you should be able to adjust it there. You set the
subscription rate in the OPC client, and the OPC server will give
updates according to this schedule. There's no theoretical lower
limit. How often the Citect server polls the PLC however, will
determine how fresh the data is.
If the server's poll time is slower than the OPC requests, then
stale data will be provided to the client. When caching is enabled,
all data that is read from a I/O device is stored temporarily in
the memory. A minimum cache time of 300 milliseconds is
recommended. If you are caching for 300ms, and requesting data via
OPC every 100ms, then you will get 3 sets of the same data.
So feel free to adjust the update rate, but beware of the Citect
server poll rate also. |
