FB_DynMem_Manager
This function block provides the possibility to dynamically allocate memory and to release it again. Integrated counters indicate the memory consumption and thus enable an overview of the already allocated memory.
It is entirely up to the user to decide whether an instance is used across the entire application or whether several individual instances are used for different program parts. With larger applications, the latter may be advantageous in the case of diagnosis. This function block is capable of multi-tasking and an instance can thus be used from various task contexts.
If the function block determines that not all of the allocated memory has already been released when shutting down the PLC, an error message is sent as an event to the TC3 Event Logger.
Properties
nAllocatedSize: indicates the current size in bytes of memory allocated with this function block instance.
nBufferCount: indicates the current size of buffer allocated with this function block instance.
nObjectCount: - future reserved -
Methods
Alloc():
This method dynamically allocates memory and returns a pointer to this memory block. If allocation fails, e.g. because no free memory is available, the method returns ZERO.
An indication is given next to the desired size in bytes, stating whether the memory block should be zeroed.
The dynamically allocated memory can be used for individual data or data blocks. It cannot be used for dynamic instantiation of function blocks.
METHOD Alloc : PVOID
VAR_INPUT
nSize : UDINT; // requested size in bytes
bReset : BOOL; // zero the allocated memory
END_VAR
Free():
This method releases previously allocated memory again. The memory block must be allocated with the same function block instance beforehand and the size of this memory block must be specified.
METHOD Free
VAR_INPUT
p : REFERENCE TO PVOID; // the given pointer is reset to zero after deletion
nSize : UDINT;
END_VAR
Requirements
Development environment | Target platform | PLC libraries to include |
|---|---|---|
TwinCAT v3.1.4024.7 | IPC or CX (x86, x64, ARM) | Tc3_DynamicMemory |