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Update time for process images

11/25/2024 9:16 AM	Rate (0)
ZHK Bronze Member Joined: 2/18/2013 Last visit: 11/18/2025 Posts: 145 Rating: (12)	Hello, In reviewing the data for estimating process image partition update times, I observed that the copy time for PROFIBUS I/O does not seem to vary with the network speed. Why is there no dependency between the PROFIBUS network speed and the copy time per word? Shouldn't higher speeds impact the time required for data transmission and processing? Looking forward to insights from the community! Specific page in the document - Page 16 (see attachment); Full document - link Attachment Update time for process images.pdf (231 Downloads)
	Last edited by: ZHK at: 11/25/2024 10:38:05 Last edited by: Moderator_Lan at: 11/25/2024 12:20:48 link optimized
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11/27/2024 12:48 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 1/16/2026 Posts: 3054 Rating: (1062)	ZHK In reviewing the data for estimating process image partition update times, I observed that the copy time for PROFIBUS I/O does not seem to vary with the network speed. That is indeed observed correctly ZHK Why is there no dependency between the PROFIBUS network speed and the copy time per word? Shouldn't higher speeds impact the time required for data transmission and processing? Be it OB1 process image or OBxx process image partition, these are internal memory areas that are simply updated with the most recent values prior to the OB call. In other words and as per FAQ 18325417 "The contents of the process image (PII and PIQ) do not reflect the actual values of the inputs/outputs, but the values at the time the process image was updated". As such, the PROFIBUS Network speed does not matter and the values on the Network may in fact change multiple times in between Process Image (partition) updates.
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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