Siemens SINUMERIK 840D sl Function Manual page 1338

Detailed description
2.7 Structure and functions of the basic program
Figure 2-15
Note
If the number of PLC machine data used is increased later, then DB20 must be deleted
beforehand. To prevent such extensions in use having any effect on the existing user
program, the data in DB20 should be accessed in symbolic form wherever possible, e.g., by
means of a structure definition in the UDT.
Interrupts
400120
Explanation
Response
To correct or
avoid errors
Continuation
64
DB 20
Delete DB 20 in PLC and restart
DB length is not the same as the required DB length
Interrupt display and PLC Stop
Delete DB 20 followed by RESET
After cold restart
Basic logic functions: PLC basic program solution line (P3 sl)
Function Manual, 11/2006, 6FC5397-0BP10-2BA0