Glossary
S7-300 Automation System Module data
Manual, 08/2006, A5E00105505-04
Glossary-3
Cycle time
Denotes the time a → CPU requires for a single execution of the → user program.
Default setting
A useful setting which is used whenever the user does not enter a different value.
Destruction limit
Permissible limit of the input voltage / output current. The accuracy of measurements may
deteriorate if this limit is violated. If the destruction limit is considerably exceeded, this may
destroy the internal measuring circuit.
Diagnostic interrupt
Module diagnostics function report errors to the → CPU by means of diagnostics interrupts.
The CPU operating system calls OB 82 when a diagnostics interrupt is generated.
Diagnostics
Generic term for → System diagnostics, hardware error diagnostics, and user-specific
diagnostics.
Diagnostics buffer
The diagnostics buffer represents a backup memory in the CPU, used to store diagnostics
events in their order of occurrence.
In STEP 7 (PLC → Module status), the user can read data from the diagnostics buffer to
determine the precise cause of error.
Diagnostics data
All diagnostics events are logged at the CPU and entered in → Diagnostics buffer. If an error
OB exists, the buffer is started.
Direct access
Denotes access of the CPU to a module via the → backplane bus, while bypassing the →
Process image.
electrically disconnected
The reference potential of the control and load voltage circuits at electrically isolated IO
modules are isolated galvanically, for example, using optocouplers, relay contacts or
transformers. IO circuits can be connected to a common reference potential.
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