4/11/2019 2:01 PM | |
Joined: 9/27/2006 Last visit: 10/14/2024 Posts: 12287 Rating: (2685) |
Hello; To add to Hulzhex's detailed information on the subject, have a look at the following document, showing how to configure the data exchanges of the DP-master with a DP-slave, both being S7 CPUs. DP link between CPU 315-2DP (slave) and S7-400 (master) with STEP 7 V5.3 https://support.industry.siemens.com/cs/ww/en/view/6518822 You can easily use the sample project as a basis for your own, changing the CPUs in the example with your own. Hulzhex's information on SFC 14/SFC 15 is very important: you must use them only for data exchanges greater than 4 bytes (DWord, REAL or DINT variables are already considered consistent per length) [Note: also for exactly 3 bytes of data, if this happens]. The sample project gives programming examples for their use. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 4/11/2019 2:02:39 PMLast edited by: dchartier at: 4/11/2019 2:03:07 PM |
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4/11/2019 8:00 PM | |
Joined: 9/27/2006 Last visit: 10/14/2024 Posts: 12287 Rating: (2685) |
Hello; You are trying to send 16 bits and receive 16 bits over a Profibus connection. This is the equivalent of 2 bytes IN/ 2 bytes OUT. SFC 14 and SFC 15 only allow 3 bytes or 5 bytes and more to be transmitted. For 2 bytes (a word-sized register address) you must use Load/Transfer (Move) instructions. For 4 bytes (a dword-sized register address) you must use Load/Transfer (Move) instructions. For the transfer of 5 bytes or more as consistent data (data that will be transmitted in a single Profibus transmission) then you can use SFC 14 and SFC 15. If you try to send a smaller value of registers then your SFC 14 (and SFC 15) will fail with a specific error code, which you can read in your program. The link provided earlier to a sample program gave you explanations. The attached extract from the System and Standard function manual will explain in more detail. https://support.industry.siemens.com/cs/ww/en/view/44240604 Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 4/12/2019 12:22:33 PM |
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