I/O System S900
Communication Interface for PROFIBUS DP, CI920
positive response. Otherwise, a negative response is returned, together with
the respective diagnostic message.
The S900 can start cyclic data exchange even if there is a mismatch between
the set and the actual configuration.
As a result, the project planning can be made on the basis of the planned final
configuration, without requiring that the respective I/O modules are actually
present. S900 will provide the configured default values for the missing
modules.
Re-configuration in online mode
This term refers to an uninterrupted download of a set configuration (HCIR-
Hot configuration in run mode). The HCIR configuration is mandatory for
adding, removing or replacing I/O modules without affecting the actors of I/O
modules that are not involved.
The S900 System accepts a new Check_Cfg telegram while it is running.
When the system is re-configured, it leaves the DataExchange state for a short
time (due to PROFIBUS requirements). During this time, the outputs
maintain their last value until returning to the DataExchange state. If the
online re-configuration procedure cannot be terminated properly, e.g. when
the PROFIBUS communication is interrupted, the outputs are set to their
default values. The S900 System is, thus, HCIR-compatible, without any
limitations.
Note: The non-cyclic V1 services used in many PROFIBUS devices are only
suitable for online re-parameterization. They cannot be used for modifying a
slave's configuration (i.e. its I/O data setting).
Uninterrupted download from the S900 System is only possible if the master
supports the HCIR configuration as well. However, many old master system
versions require a reboot which, of course, does not allow for online re-
configuration. Modern master systems like Symphony CMC60 or AC800F
from ABB are not limited in this way and are best suited for online re-
configuration.
If the application in the PLC or OCS is to be protected against unwanted
signal failures or alarms during online re-configuration, their engineering
24 3BDD010422R0101
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