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HOME >> Introduction of Siemens S7-300 / 400 PLC ob-fb-fc-db block
Introduction of Siemens S7-300 / 400 PLC ob-fb-fc-db block
Source: | Author:pmo89cafb | Published time: 2020-10-26 | 1772 Views | Share:
The PLC user program structure of Siemens S7-300 / 400 is obviously different from that of S7-200. The linear structure, function calling structure and structured programming can be used.
When using calling structure and structured programming, program appears in the form of organization block (OB), program block (FC), function block (FB), system program block (SFC), system function block (SFB), data block (DB). Among them, organization block (OB), program sequence block (FC), function block (FB) are collectively referred to as "logic block"; system block (SFC) and system function block (SFB) are collectively referred to as "system block".

Tissue block (OB)
Organization blocks (OB) provides the interface between the internal CPU operating system and the user program in PLC. It is a logic block directly called by the CPU operating system, which is used to manage the call and execution interruption of each component in PLC program. OB determines the structure of PLC user program and the calling order of blocks, and plays the role of "managing" user program.