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analog output monitoring in VAT table

Created by: vickyrocky at: 12/1/2009 4:54 PM (4 Replies)

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12/1/2009 4:54 PM	Rate (0)
vickyrocky Posts: 2 Rating: (0)	I also have the same query. only thing is that I am aware that you can copy the analog output to a Memory location & monitor the memory location instead.But my question is why a input can be monitored & output cant.
vickyrocky Posts: 2 Rating: (0)	Last edited by: O_Moderator at: 12/2/2009 8:33 AM new subject after splitting from /tf/WW/en/Posts/34323#top
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12/1/2009 6:55 PM	Rate (0)
Ayman Elotaify Platinum Expert Joined: 5/28/2008 Last visit: 6/6/2023 Posts: 4448 Rating: (827)	Dear vickyrocky, If you wrote in VAT, PQW300 for instance, you will not able to monitor this value. You can move it to memory area and then monitor it. To avoid this method, you can go to HW config, change the addresses of analog outputs to be inside the process image of the CPU. For example; PQW 300 became PQW 30.and then go back to VAT and write QW30 Note I have eleminated here the letter "P" Then you will be able to monitor it! Regards
	Ayman Elotaify
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11/25/2016 11:18 AM	Rate (1)
banconi Silver Member Joined: 3/19/2010 Last visit: 5/21/2023 Posts: 435 Rating: (12)	Hi, this is old post but still valid subject. I have just got one Profinet device that doesn't allow its addresses to be within the Process Image. Thus, in some cases, it is impossible to use the mentioned method, to change PQW to simple QW.

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11/25/2016 12:19 PM	Rate (0)
Piotr.M Platinum Expert Joined: 6/24/2013 Last visit: 5/25/2023 Posts: 1505 Rating: (388)	Hi This is because operation to/from PIW/PQW determines what is done i.e. Reading from Peripherial is ALWAYS reading from Peripherial INPUTS Writing to Peripherial is ALWAYS writing to Peripherial OUTPUTS. The circuitry decides what to do - when write strobe is set or when read strobe is set. This is why PLC is unable to read PQWs and write to PIWs.

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11/25/2016 3:45 PM	Rate (0)
Piotr.M Platinum Expert Joined: 6/24/2013 Last visit: 5/25/2023 Posts: 1505 Rating: (388)	REF PQW-->QW in VAT: This will work when your outoput is in process image area. it will not work when your output is outside of process image area. Length of Process Image depends on CPU and in case of some CPUs can be configured in HW Config.

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