SF/BF

Hi experts,

i need help

i have a profibus network with cpu 314c 2dp as master with 15 slaves

the master SF/BF leds are on while on slaves only BF led is on.

the massage on diagnostic buffer reads " I/O accesss  error  writing.

P area, word access; acess adress ;324. requested OB;I/O acess error OB (OB 122).

PLS i dont know what to do.

Hello nanchi;

BF stabnds for Bus Faullt: an error occured on the network.

SF stands for System Fault, which could stand for any internal problem in the CPU, such as accessing an unreachable address in a block (FC, FB..), or a programming error... Depending on the diagnostic OB that is called for the fault (as shown in the diagnostic buffer messages) you can determine what type of error occured.

First, are all the slaves showing the BF LED active? That would indicate a complete failure of the network, often due to lost termination on the end points of your network.

Very oftem, the SF that appears at the same time as the BF means that your program is trying to access data from slaves that are no longer reachable, therefore a SF fault appears.

So first check the diagnostic buffer of the CPU; for example, open the HWConfig, go online, click on any module that shows a red slash icon (inficating error), even the CPU. That opens the diagnostic buffer for each fault modue, ans  you can see (sans Save) the messages logged for these modules.

If you save the messages from the cPU and post the text file here on the forum as an attachment, we can probably help you understand the messages and identify the possible source of the fault.

For Profibus-DP troubleshooting, especially if it is the first time, you might need some guidance. I can suggest this document:

PROFIBUS fault finding and health checking

Hope this helps,

Daniel Chartier

hello sir,

i have  checked my terminations on the two ends i think they are ok, and i still have SF/BF on cpu and BF on  all the slaves. the attachement is the massege on the diagnostic buffer on the cpu. pls help.

nanchi

hello sir,

i have  checked my terminations on the two ends i think they are ok, and i still have SF/BF on cpu and BF on  all the slaves. the attachement is the massege on the diagnostic buffer on the cpu. pls help.

Hello nanchi,

Well, regarding the Diagnostics, to me it looks like a communication problem caused by a hardware failure too. The PLC has 1 write and 9 read errors. Can you please give us an overview of the network setup. Also indicate the stations which are having a BF.

Are there repeaters in the network? Are they okay?

Your PLC date is at 1994. Does it help to change the time and date to the current time and date?

Regards,

Alex

HI sir,

when i open the hardware c onfiguration online all the slaves have a red slash on thier icon including the master.

8 slaves( ET200S) has BF

5 slaves (paker ssd drives), the module led ison ,network led is of on thier technology option (profibus dp)

HMI displays ##### insted of values.

no repeaters on the network,

master cpu has SF/BF on 

nanchi

HI sir,

when i open the hardware c onfiguration online all the slaves have a red slash on thier icon including the master.

8 slaves( ET200S) has BF

5 slaves (paker ssd drives), the module led ison ,network led is of on thier technology option (profibus dp)

HMI displays ##### insted of values.

no repeaters on the network,

master cpu has SF/BF on 

Hello nanchi,

Thanks, but I suggest you to take a screenshot from the network and show it to us. One screenshot can show us more than you can tell.

Like I said earlier: the problem must be hardware. Check your cables, check your connectors, check your terminator switches, try to reboot your PLC if possible, etc.  

So please, go out and check your network.

Regards,

Alex

yes i found it,

it was a bad connector within the network, which was permanently open,

thanks alot.