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CONVERTING FLOATING POINT NUMBER TO INTEGER NUMBER, WITHOUT RND AND TRUNCATE

11/29/2007 2:43 AM	Rate (0)
Ady Posts: 43 Rating: (1)	Hello! Do you know a trick to convert a 32- bit floating point number IEEE to a 16-bit integer number (or 32-bit integer) without using the instructions RND and TRUNCATE? Thank you so much in advanced. Best regards,
Ady Posts: 43 Rating: (1)
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11/29/2007 5:59 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/1/2024 Posts: 12292 Rating: (2690)	Hello Ady; First, I would be very interested to find out why you would want to program your own conversion tool, as it is not a simple thing to do. And a PLC is not the easiest beast to program this on; STL would be the only way to go. By the way, if you can't or won't use TRUNC or RND, In Step 7 there are also FLOOR and CEILING instructions that could do the job... Now, to start with, look at the IEEE floating-point number definition (from Wikipedia): http://en.wikipedia.org/wiki/IEEE_754-1985 Here are some sites with converters and converter logic for PCs (linux and Windows) from HEXA to decimal floating-point : http://babbage.cs.qc.edu/IEEE-754/32bit.html http://www.61131.com/download.htm http://citeseer.ist.psu.edu/goldberg91what.html http://support.automation.siemens.com/WW/view/en/23803063 Up till now, I have found no code for PLCs to do a truncation of a floating-point value, and I have not much time to work on this. Here are links to C-code for a conversion to integer value: http://www.cs.tut.fi/~jkorpela/round.html http://www.mega-nerd.com/FPcast/ Try applying the logic, when you hit a snag come back to us, we'll see if we can help. Hope this helps, Daniel Chartier
	Last edited by: O_Moderator at: 9/16/2010 3:10 PM link edited Last edited by: dchartier at: 29.11.2007 06:00
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11/29/2007 10:45 AM	Rate (2)
Aret Posts: 2348 Rating: (264)	I agree - better to use standartconversiontools. But it's not so hard actually. Code below does such conversion for numbers <2^23. With little modification it can be used for any numbers. L #Real_numeber AD DW#16#7FFFFF OD DW#16#800000 T #Tmp_result // mantissa stored here L #Real_numeber AD DW#16#7F800000 SRD 23 L 127 -I JPZ posm // if exponent <127 => number <1 => result =0 L 0 T #Result BEU posm: NOP 0 // defining by how mush mantissa should be shifted L 23 >I JC err TAK -I L #Tmp_result SRD T #Result BEU err: L 0 T #Result
Aret Posts: 2348 Rating: (264)
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11/29/2007 1:18 PM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 11/1/2024 Posts: 12292 Rating: (2690)	Looks good, Aret. Regards, Daniel Chartier

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11/29/2007 5:08 PM	Rate (0)
Ady Posts: 43 Rating: (1)	Hello! Thank you so much, I wanted to do this because I´m migrating a program from s5 to S7, and there is a function in S5 that converts the floating number to integer number, this is GFD, and when you migrate the program the S7 replace with a RND.... But the logic program use it´s the next (an add of 0.5): OPN #DBIN // INPUT DB L #DDIN // FLOATING POINT VALUE L #SCAL // SCALING FACTOR *R L 5.000000e-001 // ADD 0.5 SINCE GFD TRUNCATES +R RND OPN #DBOU // OUTPUT DB T #DWOU And give me a different result in the HMI, for example, in the PLC puts a value of 162, and the HMI 163, so I wanted theycould be a little equal.... Thank you for this valuable information, you are sointelligent !! Thank you so much to both. See you!
Ady Posts: 43 Rating: (1)
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