Data register

Byte order: little endian

Cannot be used for outputs, can be used within the PLC only.

For 32-bit data: DDT4 occupies DT4 (low) and DT5 (high)

For 64-bit data: LDT4 occupies DT4 (lowest) and DT5, DT6, DT7 (highest).

For PLCs other than the FP7, the data registers from 9000 or 90000 are special data registers which can be accessed via system variables.