Data block (DB)
Data blocks (DB) is a data storage area used to store the data needed to execute user programs and the results of program execution. Its function is similar to flag register, but it has more numbers. According to different purposes, data block DB can be divided into two types: instant data blocks (DI) and general data blocks (DB).
The immediate data block (DI) is used to transfer the parameters of the function block and can only be accessed by the specified function block FB. When calling the function block FB, the immediate data block Di for the function block must be specified at the same time. The data in the real-time data block can be generated automatically, and they can be the data in the FB variable declaration table (excluding temporary variables).
General data block (DB) is used to store the global data of PLC. All FB, FC or ob can read and write the general data block. Therefore, it is also called shared data block. The data in the general data block is not deleted at the end of the user program.