Product : ISaGRAF 3.22 and +
File : extend.Extended variables and their limitations.htm
Subject : Extended variables and their limitations
Keywords: Extended Variables (over 4095) - Variable number limit
Target version 3.22 main feature has been to get over the limits
of 4095 variables per type. Variables have hence been extended.
Please note that the variables have been extended for enhancing user
This brings some limitations for their use on the target.
Here below is a summary of the limitations:
- IO variable limit has not been extended on the target side.
The new limitation does only concern internal variables.
--> Hence standard requests for locking IOs does not work including
visualization of list of locked IOs from the debugger
--> Hence if a problem occurs on such an IO, the target will return
an error but with wrong indication on the incriminated variable
- Number of steps and transitions limit do remain the same: 4095
- If division by zero occurs, the kernel normally returns the VA of
the faulty variable. The kernel returns a wrong value on the
- For asynchrounous server, when to get VA from user address for
extended variables, the function will return '0' value.
The function does not get back this value.
This also applies to modbus requests on network addresses of
- It is not possible to write a list of extended VA variables
through the asynchrounous server.
The function interface does not allow it.
- New extended requests has been added to the debugger communication
protocol to Read/ Write (including list) extended variables.
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