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very slow response in the communication with S7-300

Created by: xarisss at: 5/19/2009 11:42 AM (4 Replies)

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5/19/2009 11:42 AM	Rate (0)
xarisss Posts: 43 Rating: (0)	Hello to everyone, I had a problem last week with an MP277, which had communication with a CPU314 through MPI. The problem was that although the HMI read quickly the PLC values, it was very slow (2 seconds approximately)in writing a value. To make this more clear, when an alarm came from the PLC, the HMI showed it in less than a second. When i acknowledged the alarm, the PLC received the value after about 2 seconds.The same happenned when i triggerred another value (a PLC memory bit)through an HMI button. I pressed the button and the bit changed its state after 2 seconds. Note that the acquisition time is 100ms and the scan cycle time of the plc is 70ms. The program i am speaking about had 350 tags declared in the HMI configuration, through WinCC flexible (WinCC flexible 2007 HF4). Yesterday, i made a new program for the same HMI, with less tags (about 40). I have the same CPU. The acquisition time is the same and the scan cycle time of the cpu314 is about 23ms. I noticed that now i don't have a delay, and the HMI is more quick in writing to the PLC. Does anybody know why is this happenning? Thanks in advance.
xarisss Posts: 43 Rating: (0)
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5/19/2009 1:53 PM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 9/14/2023 Posts: 8592 Rating: (1132)	Dear xarisss, Perhaps this link, might help: http://support.automation.siemens.com/WW/view/en/23818213 Try to use in a screen tags, with follow up addresses. Example MW0, MW2 etc. Then it will give one call to CPU. When you use MW0 and MW4, it will have two calls to CPU. Best regards, Wizard

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5/20/2009 2:21 PM	Rate (0)
xarisss Posts: 43 Rating: (0)	Well, the problem of my system is that i make many calls of different words od Data Blocks. I will make a try to reduce this in half. However, before i do this, why the HMI reads so quickly the change in a value and is so slow to write to a value? (when a signal changes its state the HMI shows the alarm simultaneously. when i press a button of the HMI in order to acknowledge, or to switch on a lamp, i have a delay of 2 seconds)
xarisss Posts: 43 Rating: (0)
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5/20/2009 4:47 PM	Rate (0)
xarisss Posts: 43 Rating: (0)	I tried FC630.I see that it has 2 inputs TSB and TS2. Which one is TSx? The default one in the sample program is TSB=B#16#4 and TS2=B#16#6. Although i change the values, i don't see any significant change in the cpu scan cycle time. Has anybody used FC630 before?
xarisss Posts: 43 Rating: (0)
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5/26/2009 8:45 AM	Rate (0)
Wizard Diamond Expert Joined: 4/24/2006 Last visit: 9/14/2023 Posts: 8592 Rating: (1132)	xarisss (when a signal changes its state the HMI shows the alarm simultaneously. when i press a button of the HMI in order to acknowledge, or to switch on a lamp, i have a delay of 2 seconds) Hi, The difference can be the used Update Cycle time. Best regards, Wizard

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