Siemens CPU 313C Hardware And Installation Manual page 160

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System errors can occur especially in the &RPPLVVLRQLQJ phase. Tracking these
errors might be a time-consuming effort, since they can occur likewise on hardware
and on software side. Here, the multitude of testing functions ensures
commissioning without problems.
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Faults GXULQJ RSHUDWLRQ are almost always caused by hardware errors or damage.
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Errors the S7 CPUs can recognize and to which you can react with the help of
organization blocks (OBs) can be split into the following two categories:
• Synchronous errors: Errors you can relate to a specific point in the user
program (e.g. error when accessing a peripheral module).
• Asynchronous errors: Errors you can QRW relate to a specific point in the user
program (e.g. cycle time exceeded, module error).
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Programming with foresight and, above all, knowledge and proper handling of
diagnostic tools puts you into an advantageous position in error situations:
• You can reduce the effects of errors.
• It makes it easier for you to locate errors (e.g. by programming error OBs).
• You can limit downtimes.
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SIMATIC S7 hardware offers diagnostics with LEDs.
These LEDs are implemented in three colors:
• Green LEDs report regular operation (e.g. supply voltage is applied).
• Yellow LEDs indicate special operating states (e.g. "Force" is active).
• Red LEDs report errors (e.g. bus error)
A flashing LED also indicates a special event (e.g. memory reset).
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Notes on diagnostics with LEDs are found in the Chapter below.
Notes on diagnostics of I/O modules capable of diagnostics are found in the
relevant Manual.
11-4
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03