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Browse Questions » Decentral Peripherie: Dp Analysis (SFC13) trouble Upon 318-319 Central Processing Unit

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Asked:20 Oct 2025

Decentral Peripherie: Dp Analysis (SFC13) trouble Upon 318-319 Central Processing Unit

Greetings,
I am having no luck using SFC13 to read the DP slave diagnostic data on a 318 and 319 CPU. The strange thing is that the same code does work and reads the diagnostics on a 315.
The way I have set this up is to set the "REQ" bit for SFC13 in OB82 and OB86 based on whether it is an incoming or outgoing event. The actual call to SFC13 is in OB1. To reset the REQ bit, I use the negative edge of the BUSY bit from SFC13. With this I am monitoring a simple ET200s slave.
The only obvious difference between using the 315 and (318or 319) is that in the 315 the diagnostic address is low (3FE) and in the other 2 it is higher (1FFC).
With the 315, I pull the PM out of the ET200s and the data block shows the codes with no problem. The same thing on the 318 and I get absolutly nothing (data block is empty).
Any help would be GREATLY appreciated!!!

#sosflex #Decentral Peripherie #siemens
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Answers(1)
Siemens Test Added an Answer on20 Oct 2025

SFC13 Diagnostic Read Issue - 318/319 vs 315 CPU

Greetings! Siemens Self Support here, integrated with SiePortal. I understand you're experiencing issues reading DP slave diagnostic data using SFC13 on 318/319 CPUs, while it functions correctly on a 315 CPU.

The differing diagnostic address (3FE on 315 vs. 1FFC on 318/319) is a key indicator. This suggests a potential issue with how the address is being handled by the larger CPUs.

Possible Solutions & Considerations:

  • Address Range Check: Double-check that the address 1FFC is a valid diagnostic address for your specific ET200S module and firmware version on the 318/319. Refer to the ET200S hardware configuration list.
  • Data Type Compatibility: Ensure the data type used in your data block for receiving diagnostics is appropriate for the address range (1FFC). Sometimes, larger addresses require different data type handling.
  • OB82/OB86 Triggering: Verify that the REQ bit triggering in OB82/OB86 is functioning identically on all CPUs. Although it works with the 315, confirm no subtle differences in execution due to CPU variations.
  • SFC13 Parameter Check: Carefully review all SFC13 parameters – module address, diagnostic type, and data length – ensuring they are consistent across all configurations.

Further Support:

For detailed troubleshooting and access to the SiePortal knowledge base, please visit: Siemens Industry Support Portal. Specifically, search for articles related to "SFC13 diagnostic read" and "ET200S diagnostics". Consider submitting a support request with your project details and CPU/module firmware versions for more specific assistance.

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