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5.2 CC-Link Module Access Function
5.2.1 Block data assurance per station
5
ACCESS VIA NETWORK MODULES
(3) How to read out cyclic data (from the buffer memory)
Cyclic data can be read out from the buffer memory using the block data assurance
per station, by one of the methods described below.
If any other method is used, integrity of cyclic data for each slave station is not
guaranteed.
1) Enable the bock data assurance per station in CC-Link utility.
2) Use either of the following methods.
(a) Automatic cyclic data refresh
1) Execute the QBF_FromBuf function with "automatic" specified for "CC-Link
refresh method" of the third argument (ulOffset).
2) In the timing of the next link scan, refreshed cyclic data (in the buffer memory)
are read out.
User program processing is suspended until the reading is completed.
3) Upon completion of reading, the user program processing resumes.
During execution of the QBF_FromBuf function, a time of up to one link scan may
be spent for standby.
Table 5.3 Reading out cyclic data (from the buffer memory)
Method Description See
Automatic cyclic data
refresh
Only by executing the QBF_FromBuf function, data are
automatically refreshed and read out (in the next link
scan).
(a)
Manual cyclic data refresh
Data are manually refreshed with the
QBF_RefreshLinkDevice function, and then they are
read out by executing the QBF_FromBuf function.
(b)
Figure 5.2 Readout operation
User program
Buffer memory
Link scan
C Controller module CC-Link module
Refresh
: User program is in standby state.
Link scan
Refresh request
1)
2)
3)
Reading data
QBF_FromBuf function
(Automatic)
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