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CONV instruction

Created by: Homeroid_BL at: 10/1/2010 1:56 PM (5 Replies)

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10/1/2010 1:56 PM	Rate (0)
Homeroid_BL Posts: 211 Rating: (6)	Hi all! Since S7-1200 manual is very poor, and Step7 Basic has no simulation,I want some of you to answer this question: If I use CONV instruction, to convert WORD to REAL, and if input WORD is 7FFF, what is the value of REAL output?
Homeroid_BL Posts: 211 Rating: (6)	Last edited by: Homeroid_BL at: 10/1/2010 1:57 PM
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10/1/2010 2:39 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/23/2025 Posts: 15555 Rating: (2467)	It should convert to 3.2767E+04 Or, if you wish, 32767.0 Yes, the manuals are quite lacking, specifically about the lack of usage examples. The CONV instruction is a no frills block. I could load it into a PLC and run it, but to be honest, if you are worried about a CONV instruction, you will not be at all happy with your S7-1200 programming experiences. This is probably amongthe simplest and most useful blocks. It simply does what you want it to do. Be sure to check the ENO state if you have a chance of bad data causing problems in your PLC program.
	science guy
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10/1/2010 3:05 PM	Rate (0)
Homeroid_BL Posts: 211 Rating: (6)	I also know that it SHOULD... but, would it? Thanks. I still do not know, as for 7FFF as for 8000.
Homeroid_BL Posts: 211 Rating: (6)
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10/1/2010 3:31 PM	Rate (0)
Denilson Pegaia Platinum Expert Joined: 9/23/2005 Last visit: 1/22/2025 Posts: 4396 Rating: (1464)	Hi, it's look like that you are working with analogical signal. 7FFF is a overflow situation. For Analogical handling, I suggest you use a read for use blocks avalible on the link: /tf/WW/en/Posts/31698
	Denilson Pegaia Siemens Industry Sector Technical Support
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10/1/2010 5:39 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/23/2025 Posts: 15555 Rating: (2467)	PLC loaded with CONV 16#7FFF to REAL returns 32767.0 PLC loaded with CONV 16#8000 to REAL returns 32768.0 Again, if you are worried about the CONV function, you will have bigger problems as many other Siemens supplied function blocks are more trouble than the care-free CONV block. Oh yes, if you are testing a PLC, be sure to include fault monitoring for your CPU analog inputs, or turn off overflow monitoring (unless you wire them to a voltage within their operating range of course). CPU will not stay in RUN mode ;) Now as to _why_ you want to know about those values... Pegaia posted their thoughts on why you might be asking. If you are looking at comparing the REAL values for over/under flow,etc., I would suggest checking prior to the conversion. Hope that helps.
	science guy
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10/1/2010 6:01 PM	Rate (0)
Homeroid_BL Posts: 211 Rating: (6)	Thanks, huggy_d1, for your time (loading at PLC), anh thanks Pegaia too. There is no need to worry about me, I program Omron and Simatic controllers for 15 years. I know much about formats, I just wanted to be sure (on real PLC) that function works as expected. I say so, because last year, for example. I had much trouble with FDL communication functions on S7-300 -I downloaded it from Siemens site, but functionsdid not work as expected (and described in manual). I had much time for debbuging, so I managed to put it in work. This time, with S7-1200, there will be no time for debbuging, program must work immidiatelly - I will see S7-1200 for the first time at downloading time. Best regards.
Homeroid_BL Posts: 211 Rating: (6)
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