Rockwell Automation T8xxx Application Note Trusted Intelligent Online Updates - Manual (Page 23)

Trusted TM
AN-T80009 Trusted
TM
Intelligent Online Updates
Issue 4 Nov 08 AN-T80009 23
will delete the update history and prevent the next change from using an intelligent online update. If the
application is taking too much disk space (or is too big to archive), reduce the number of non-protected
historical snapshots that it keeps, and delete snapshots that are no longer relevant.
1.13.12. Real inline constants
A REAL in-line constant does not update properly during an Intelligent Update. A REAL in-line constant
is defined by adding a variable tag in the FBD editor, but specifying a numeric value instead of a
variable name. It can also be defined by using a REAL textual value in ST. In either case, it is not the
same as defining a CONSTANT type variable in the dictionary and using that variable by name.
When a REAL in-line constant is modified in the source (either FBD or ST) and a new compilation is
made, a regular online update will result in the new value for the constant being used. When an
Intelligent Update is performed, the value of the REAL in-line constant remains unchanged. Note that
this behaviour only holds for REAL in-line constants, as INTEGER and BOOLEAN in-line constants
take on their expected values after an on-line update (either a regular update or an Intelligent Update).
The cause of this is due to the difference in how ISaGRAF generates variables for in-line constants.
For INTEGER and BOOLEAN constants, a global temporary variable is generated, and the initial value
for that variable is set to the specified constant. For REAL in-line variables, ISaGRAF generates a local
temporary variable with an initial value equal to the value specified for the constant. The difference is
subtle: a change to an INTEGER or BOOLEAN in-line constant will result in the generated code
referencing a different variable (i.e. one for the new in-line constant value), but a change to a REAL in-
line constant doesn't.
1.13.13. Don’t Update Later
Prior to MP firmware release 3.5, if an update download is set to ‘Update Later’ and is stopped halfway,
e.g. by breaking the comms or closing the debugger window, it is possible to ‘realise’ this half
application once reconnected. Note that using ‘Update Later’ is not recommended because the
application may not be updated at that time and may be remain to be inadvertently updated at a later
session; it is far better to load and ‘Update Now’ in one go.
1.13.14. Processor hot swap and online update
It is recommended for systems prior to release 3.5 to remove a standby MP during an update. If a
processor hot swap occurs during an online update, the system may shut down I/O or be unable to
perform another handover.
1.13.15. Counting Timer and update
Prior to release 3.5, active timer variables are updated in a manner that causes their values to be
corrupted.
1.13.16. IOU Manager Options
It is recommended to check all the options in the Online Update Manager options window. These
options provide valuable information on the change and its likely success including the DELETED and
NEW messages described above.
1.13.17. CRC Differences
The ‘Normal’ online update relies on calculating the CRC of the application symbol table (variable data
space) and comparing this between the running and potential versions. If the CRCs are the same, then
a normal update is allowed. Different installations of the Toolset may result in an internal re-ordering of
data resulting in a different CRC for the same application. This will prevent a normal update from a
new PC with a copy of the running application if the CRC calculates differently. Note that with Intelligent
updates enabled, in this situation the update will automatically be carried out through the intelligent
update manager.