Saia-Burgess Controls AG
User Manual Standby System
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Document 27-645
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Edition E
NG 02
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2017-04-26
Process Data Synchronization
Diagnostic
2-6
2
2.3
Process Data Synchronization
All media used by the CPU1 Redundant program are synchronized between CPU1
of the Active and the CPU1 of the Standby device.
The data can be synchronized cyclically (e.g. at the end of every cycle, all the
data are transferred and the next cycle beings only after all data has been sent),
or it can be sent asynchronously without slowing the program cycles. If sent
asynchronously, a minimum sync time can be specified, and the Standby CPU’s
data may be some cycles behind the Active CPU. See
Data Synchronization and Switchover
for timing details. The data synchronization behavior is defined
in the Device Configurator for the Redundant CPU1, see
.
The PG5’s “build” generates a table of all the used media addresses, and saves
the first and last used addresses for each media type.
All media between the first used address and the last used address are
transferred, even if the data is not used by the program, so try to keep the
addresses consecutive.
If using dynamic addressing, keep the dynamic address ranges to a minimum the
device’s “Build Options” to assign the address ranges. Use the “Device / Advanced
> Clean Files” command to reset the dynamic address allocator so the addresses
are assigned consecutively and no addresses are unused.
If you use absolute addresses in the program, use addresses immediately before
or after the dynamic address ranges so that absolute and dynamic addresses
are consecutive. Synchronization data also includes the data in the “[From]
, so the addresses in this file should
also be consecutive.
The number and addresses of the media to be transferred are shown in Project
Manager’s “Messages” window when the Redundant device’s program is built:
The worst-case data synchronization time for 16K Flags, 16K Registers, 1600 T/
Cs, 128K RAM Text/DB (200KB data) is about 200ms. But usually the amount of
used media will be much smaller, so the sync time will be faster.
