2. Technical Description
11
The full list of when the symbolic persistent variables keep their values and when the value is lost
can be found in the Table 2-6. Besides the persistent area size declared in the Table 2-5, are reserved
these 44 bytes to store information about the persistent variables (not available for use).
The Table 2-6 shows the behavior of retentive and persistent variables for different situations in
which “-“ means the value is lost and “X” means the value is kept.
Reset warm/Power-on/off cycle
Remove CPU or Power Supply
from the rack while energized.
Reset Process (IEC 60870-5-104)
Table 2-6. Post-command Variable Behavior
In versions 1.5.0.21 and lower for NX3004 and 1.5.1.0 for NX3010, NX3020 and NX3030, the
retentive and persistent symbolic memories and addressable output variables memory (%Q) used to
have a fixed maximum size. On Table 2-7, it’s possible to consult the maximum sizes allowed in
these older versions.
In versions above the ones mentioned, the CPUs allow flexible retentive and persistent memory sizes.
For further information, refer to the section Retain and Persistent Memory Areas.
Retentive addressable output variables
memory (%Q)
Persistent addressable output variables
memory (%Q)
Retentive symbolic variables memory
Persistent symbolic variables memory
Table 2-7. Retentive and Persistent memories in older versions
In the case of Clean All command, if the application has been modified so that persistent variables
have been removed, inserted into the top of the list or otherwise have had its modified type, the value
of these variables is lost (when prompted by the tool MasterTool to download). Thus it is
recommended that changes to the persistent variables GVL only include adding new variables on the
list.
Total redundant data memory: Redundant data memory is the maximum memory area that can be
used as redundant memory between two redundant CPUs. This value is not a different memory, note
that the sum of all redundant variables (addressable input variable, addressable output variable,
addressable variable, symbolic variable, retain symbolic variable, persistent symbolic variable) must
be less than or equal to the available redundant data memory.
Program memory: Program memory is the maximum size that can be used to store the user
application. This area is shared with source code memory, being the total area the sum of “program
memory” and “source code memory”.
Source code memory (backup): This memory area is used as project backup. If the user wants to
import the project, MasterTool IEC XE will get the information required in this area. Care must be
taken to ensure that the project saved as a backup is up to date to avoid the loss of critical
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