Omron CQM1H-CLK21 User Manual
Page 360
337
Changing the Data Link Tables with Active Data Links
Section 10-2
Data link communications will continue, so the Communications Error Flag for
the data link status will not turn ON in any of the nodes in the network.
Refer to
10-2-4 Timing Required to Change Data Link Tables with Active Data
for details on timing required to change the data link
tables.
10-2-4 Timing Required to Change Data Link Tables with Active Data
Links (Theoretical)
When changing data link tables with active data links, the data refresh for the
corresponding node will stop temporarily. During that time, even if the data in
the data link send area in the PLC is refreshed, it will not be sent as data link
data to other nodes. Data received from other nodes will also not be shown in
the data link receive area of nodes with data link tables that are being
changed. The data refresh interrupt timing (maximum theoretical value) is as
follows:
Data link refresh maximum interrupt time = 2
×
Unit cycle time of the node
with data link table being changed (See note 1.) + 3
×
communications cycle
time (ms)
Note
1.
When CS- or CJ-series PLCs are being used, if the total number of data
link send words exceeds 7,800 words, this value is multiplied by 3.
2.
Consider the effect of the data link refresh interrupt time on the applica-
tions when changing the data link tables. If the maximum interrupt time is
not suitable for the user application, transfer the data link table after stop-
ping the data links from a Programming Device as before, and then restart
the data links.
Command re-
ceived to change
with active data
links
Change during
active data links
completed
Time
Data link send data
Data link receive data
Most recent data read from
Unit
Data immediately
before change
Most recent data read from
Unit.
Most recent data received
from other node
Data immediately
before change
Most recent data received from
other node
Refresh stopped
Refresh resumed
Data link area of node with the data link table
to be changed