The significance of data storage represented by DB2. DBD8 and DB2. DBX8.0 of Siemens 300plc and its differences.

The * * * shared data block in the DB block is the place where intermediate variables are stored, which is similar to the M register, except that the DB block can be artificially established, and the M register comes with the system. The background DB block is dedicated to FB to store FB operation parameters. DB2。 DBD8 indicates that the physical address of data is block 2, and the data type of DBD is real number. In 300, real numbers account for four bytes. The first address of the data is DB2. DBD8, that is, from DB2. DBD8 to DB2. DBD 1 1, while DBX8.0 indicates that the data is Boolean, that is, the switching value has only zero or one or two states. This is a bit-by-bit memory with the eighth memory address.