area length error when writing??

[Richharry]

guys,

I am trying to commission a software redundant system siemens S7 300.

the SF led's are on with both processors, looking in the diagnostic buffer it is full of area length error logs.

The description points me to the instance db's, is data being written to them which is too large??

regards
RH

 

[JesperMP]

What EXACTLY does it say in the diagnostics buffer ?

One way to locate the exact point in the program that causes the error is to delete all the error OBs. Then when the CPU faults, you can investigate the stacks and get the information where in the program the bad code is located.

 

[Richharry]

each log states:
"Area length error when writing
InstanceDB,Double word access acess address:4834- (for this log )
Requested OB: Programming error OB121
Priority cals:12
Internal error,incoming event"

event ID 16#2523

 

[JesperMP]

It sounds like some kind of indirect adressing gone bad. 4834 is an extreme number if it is supposed to be a byte offset in an instance DB.

Try the trick with removing the error OB121.

 

[Manglemender]

Priority class 12 is OB35 if that helps. When the error is highlighted in the diagnostic buffer, do you get the option of "Open"? This would take you to the source of the error.

Nick

 

[PeterW]

Rather than crash the PLC, especially if this is undesirable for the process, can't he wrote some code in OB121 to capture the information form OB121 TEMP variables.

 

[Jeebs]

Rather than crash the PLC, especially if this is undesirable for the process, can't he wrote some code in OB121 to capture the information form OB121 TEMP variables.

I believe this is what the OB was created for......

 

[Manglemender]

All the required data will be in the temp variable in OB121 and can be written to a DB for interrogation.

Nick