The data storage is used for READ_U_PCMCIA and WRITE_U_PCMCIA function blocks.

Lets say for e.g.. you configure the Data storage size as 2000 kB then the 2000 kB of data storage represents:

2000 kiloBytes * 1024 = 2048000 Bytes

Since The READ_U_PCMCIA and WRITE_U_PCMCIA functions are working with word addresses:

So 2048000 Bytes / 2 = 1024000 Words

Hence Addresses from 0 to 1024000 for the memory card can be used for data storage.

In the MAST section of the program, program as follows:
The memory card is connected into slot 0.
The WRITE_U_PCMCIA function writes 10 words to address 10000 on the memory card from %MW100.
The READ_U_PCMCIA reads 10 words from address 10000 on the memory card to %MW110.

​Representation of WRITE_U_PCMCIA and READ_U_PCMCIA in ST language:
WRITE_U_PCMCIA (0,10000,10,100,Status_write);
READ_U_PCMCIA (0,10000,10,110,Status_read);


Basically The WRITE_U_PCMCIA function transfers data from the PLC RAM memory to the user memory card archiving zone and The READ_U_PCMCIA function transfers data from the user memory card archiving zone to the PLC RAM memory. The function READ_U_PCMCIA allows addressing the PLC zone's beginning to be copied to the PCMCIA card up to 65 535.