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Siemens S5 OB Numbers Compared to S7 OB Numbers

Are the standard OB numbers the same in the S5 and the S7 software?

The standard OB numbers in the S5 are not the same as in the S7 software. Below is a comparison to explain the differences.

  S5 S7
Time-Delay Interrupt OB 6 OB 20
Cyclic Interrupt OB 10-18 OB 30-38
Programming Error 19 121
Restart - Warm Restart 20 100
Restart - Hot Restart 21 101
Access Error 23 122
Time Error 26 80
Power Supply Error 34 81
CPU Hardware Fault 35 84


The standard assignments for the code block names can be modified. For more information, please reference the S5/S7 for Windows User Guide.