Siemens SIMATIC S7-400 Installation Manual page 213

Error Display
Error display is one of the possible responses of the operating system to a run-time
error. The other possible responses include: error response in the user program,
STOP mode of the CPU.
Error Handling via OB
When the operating system detects an error (for example, STEP 7 access error), it
calls the specific organization block (error OB) for this error, where the further
response of the CPU can be specified.
Error Response
Response to a run-time error. The operating system can respond to the following
types: transferring of the programmable controller to STOP mode, calling of an
organization block where the user can program a response, or displaying of the
error.
F
FB
→ Function Block
FC
→ Function
FORCE
Function which can be used to assign fixed values to specific tags in a user
program or CPU (also: I/Os), so that the user program is not able to change or
overwrite these values. The function allows users to set defined tag values in the
user program for use in specific situations and to test the programmable functions.
Function
According to IEC 61131-3, a function is a code block that does not contains any
static data. Temporary tags of functions are stored in the local data stack and will
be lost after the FC was executed.
Functions are therefore suitable for storing data in shared DBs. Because FCs are
not assigned a memory, you always need to specify their actual parameters. You
can not assign initial values to the local data of an FC.
Automation System S7-400 Hardware and Installation
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Glossary
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