[?]: Sampling Frequency Problem with OB35

ErdemSivri · Post by **ErdemSivri** » Tue Aug 11, 2009 4:00 pm

Hello

I am having a problem with OB35 I am calling OB35 with 100Hz frequency each 10ms and sometimes PLC gives SF.
What is the real limit for OB35?

Also I have a bigger problem.
I have to produce a 6Hz sine wave with 315-2dp but I cant manage to create a proper sinewave with 100Hz. I only have 16 samples per period which is not enough.
Have anyone seen this kind of problem before?
Is there any way to overcome this problem. Thanks.

venix · Post by **venix** » Tue Aug 11, 2009 8:00 pm

Hello!

When the same watchdog interrupt is generated again while the associated watchdog interrupt handling OB is still executing the operating system calls OB80(timing error).

Time interval for trigerring 1ms to 1 minute(incremmented by 1 ms).

Best regards!
Venix

ErdemSivri · Post by **ErdemSivri** » Wed Aug 12, 2009 5:21 am

venix wrote:Hello!

Time interval for trigerring 1ms to 1 minute(incremmented by 1 ms).

Best regards!
Venix

How can I call the interrupt trigered each 1ms?
Thanks

venix · Post by **venix** » Wed Aug 12, 2009 8:06 am

Hi!

You can do this when you parameterize the CPU.
You go on HW Config(Object Hardware in S7 project)->double click on CPU3xx on slot 2->Cyclic Interrupts ->OB35

Hope this will help.

Best regards!
Venix

ErdemSivri · Post by **ErdemSivri** » Wed Aug 12, 2009 11:27 am

Hello Venix

Thanks for your reply but I get SF even at 10ms I did try 1ms with ob35 but the CPU always gives SF so your advice doesnt work. Thanks anyway.

venix · Post by **venix** » Wed Aug 12, 2009 12:47 pm

Try to increase the base!
The problem is that the execution time of the interrupt is bigger then triggering time.Tell me what is the error from Diagnostic Buffer

Best regards!
Venix

ErdemSivri · Post by **ErdemSivri** » Wed Aug 12, 2009 2:48 pm

I am not at the company right now.Tomorow the very first thing I will do is to check the diagnostic buffer and write down here. Thanks for your interest pal.

ErdemSivri · Post by **ErdemSivri** » Thu Aug 13, 2009 5:48 am

Here is what the diagnostic buffer tells us:

OB request error

No reveleance for user Z1(0000)
Cause: CYCLIC INTTERRUPT PULSE GENERATOR 6
Causing OB: OB35
Requested OB: OB80

This test is done with CPU 313C beacuse I dont have the 315 CPU right now because it hasnt arrived yet...

The interesting thing is if I dont be online in OB35 the CPU doesnt give SF I can be online in OB1 other FCs FBs no problem but not with OB35...

Thanks.

venix · Post by **venix** » Thu Aug 13, 2009 8:50 am

Hi!

Maybe when you are online the execution time is increasing.So this is the reaso why you get a timming error.

Best regards!
Venix

ErdemSivri · Post by **ErdemSivri** » Thu Aug 13, 2009 1:02 pm

I think so.

That is not a big problem also dont need to be online when everything is setup and machine begins to work.

Thanks for your help.