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

extented variables


- 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

extended variables.


- 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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