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2. Technical Description
17
Persistent symbolic variable memory:
It is the area where the persistent symbolic variables are
assigned. Persistent data keep their respective values even after a download of a new application into
CPU.
ATTENTION:
The declaration and use of persistent variables should be performed exclusively through the
Persistent Vars object, which may be included in the project through the tree view in Application ->
Add Object -> Persistent Variables. Do not use the expression VAR PERSISTENT in the
declaration field of POUs variables.
Besides the persistent area size displayed in the table above, these 44 bytes are reserved to store
information about the persistent variables (not available for use). The table below shows the
situations in which the persistent variables maintain or lose their values, as well as the behavior of
retain persistent and symbolic variables in given situations. “-” means that the value is lost and “X”
that the value is kept.
Condition
Symbolic variable
Retain variable
Persistent variable
Reset Warm /Power on
cycle
-
X
X
Reset Cold
-
-
X
Reset Origin
-
-
-
Remove CPU or Power
Supply from Rack when
powered
-
-
-
Download
-
-
X
Online change
X
X
X
Reboot CPU
-
X
X
Clean All
-
-
X
Reset Process
(IEC 60870-5-104)
=
X
X
Table 2-4. Non-volatile Variables Behavior
As informed by MasterTool at download, the Clean All command modifies the application. If the
application is changed in a way that persistent variables had beem placed on the top of the list or had
changed their type, the value of those variables will be lost. Thus, it is recommended that any
changes to the persistent variables GVL only include adding new variables on the end of the list.
Redundant Variable Memory:
Only applied to projects with CPU redundancy. It refers to the
variables that are synchronized between the redundant CPUs – addressable variables (% I and % Q)
used for I/O modules, and symbolic variables of the user program, declared in GVLs or redundant
POUs.
Program memory:
It refers to the memory area that corresponds to the maximum size that can be
used to store the user application. This area is shared with the source code memory, thus the total
area is the sum of the “program memory” plus the “source code memory”.
Source code memory (backup):
It is the memory area available to store a backup from the project.
In case the user decides to import the project, the MasterTool Xtorm software will search the
required information in this area. It is important to ensure that the backup project is updated to avoid
the loss of critical information. This area is shared with the program memory, thus the total area is
the sum of the “program memory” plus the “source code memory”.
User files memory:
This area of the memory is designed to store files, such as doc, pdf, images, etc.,
that is, it allows data recording like a memory card.
Redundancy support (same rack):
The HX3040 supports CPU redundancy when placed ate the
same rack. More information can be found in chapter 6. HX3040 Redundancy.