Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Real value assignation - STEP7

Created by: gumis at: 4/30/2009 10:21 AM (11 Replies)

Rating (3)

Thanks 2

Result pages:: |; 1 | 2; |

12 Entries

Entries per page: 10 | all

4/30/2009 10:21 AM	Rate (0)
gumis Posts: 45 Rating: (0)	Dear all, I am beginner in programming of PLC. My purpose is assignation of real value to specified memory place. What will be the difference between 10 and 10.71, for instance? I am going to use MOVE instruction.
gumis Posts: 45 Rating: (0)	Last edited by: gumis at: 4/30/2009 10:22 AM
Suggestion To thank Quote Answer

4/30/2009 12:40 PM	Rate (1)
candyengineer Silver Member Joined: 5/17/2006 Last visit: 5/10/2023 Posts: 217 Rating: (26)	Hello gumis, If I dont misunderstand you ; 1- you need to define real value 2 -use move to assign real value Best regards, Attachment 1.JPG (219 Downloads)
	Last edited by: candyengineer at: 5/21/2009 10:31 AM missed Last edited by: candyengineer at: 5/4/2009 9:33 AM Last edited by: candyengineer at: 5/1/2009 5:27 PM Genetic Fuzzy PID Controller
Suggestion To thank Quote Answer

4/30/2009 7:22 PM	Rate (0)
Eastern Posts: 557 Rating: (64)	hi L 123.575 real Value will load into the accumulator T MD0 accumulator will transfer the 32 bits real value to MD0 (real data type). find the attachment,refer page no 2 & 3 hope this will give you a more information...... regards Attachment ePRO1_08_DigitalOp.zip (97 Downloads)
Eastern Posts: 557 Rating: (64)
Suggestion To thank Quote Answer

5/1/2009 4:05 PM	Rate (0)
gumis Posts: 45 Rating: (0)	Thank you for the help. candyengineer: My purpose was writing real value to some memory space. That's very simple and I have done it. Are you sure the real values are kept on 64-bits?LAD's Programming Manual says about 32-bit IEEE floating-point numbers ( MSB-sign,23-30 -exponent,22-0 mantissa). Eastern: I understand how to make conversion from 32 bit real value in binary format to decimal one but I cannot understand how to make conversion in opposite direction.
gumis Posts: 45 Rating: (0)
Suggestion To thank Quote Answer

5/1/2009 5:03 PM	Rate (2)
candyengineer Silver Member Joined: 5/17/2006 Last visit: 5/10/2023 Posts: 217 Rating: (26)	Hello, This explains everthing Working with DOUBLE in SIMATIC Double Precision Best regards, Attachment Untitled.jpg (147 Downloads)
	Last edited by: candyengineer at: 5/1/2009 5:26 PM double precision docs Genetic Fuzzy PID Controller
Suggestion To thank Quote Answer
This contribution was helpful to 2 thankful Users dchartier gumis

5/2/2009 8:40 PM	Rate (0)
gumis Posts: 45 Rating: (0)	Thank you. Now, I understand how the real numbers are represented with 32-bit and 64-bit precision. I know how to make conversion. candyengineer: Does the real numbers in STEP7 are always placed on 4 words? When I use Double Integer to Floating-point number instruction, will I get value placed on 4 words? I do not understand the difference between your first answer in this topic and the chapter 8.1 in LAD Programming Manual. Thank you for the patience. Regards, gumis
gumis Posts: 45 Rating: (0)
Suggestion To thank Quote Answer

5/4/2009 8:58 AM	Rate (0)
candyengineer Silver Member Joined: 5/17/2006 Last visit: 5/10/2023 Posts: 217 Rating: (26)	Hello gumis , No its not, its what step7 help says in the document. Please have a Look at the attachment, It's 32bit , 2word , 4byte ... After you create datablock , you can see from its 4 byte. Also can be seen from reference table Best regards ps: sorry for first answer right one must be like this If Im not wrong , Be careful , It lays on 4words MD21 means mw21,mw23 bm21,mb22,mb23,mb24 Attachment Untitled.jpg (126 Downloads)
	Last edited by: candyengineer at: 5/4/2009 10:00 AM Last edited by: candyengineer at: 5/4/2009 9:35 AM Genetic Fuzzy PID Controller
Suggestion To thank Quote Answer

5/8/2009 8:33 AM	Rate (0)
Aret Posts: 2348 Rating: (259)	Very nice blocks to start from, but what about math fuctions? I mean i need to calculate (a+b)*c+d/e, where all a,..e are double. Couple of years ago i wrote 64bit math for such task, but maybe there is standart solution for it? I didn't find it :^(
Aret Posts: 2348 Rating: (259)
Suggestion To thank Quote Answer

5/8/2009 11:56 AM	Rate (0)
Eastern Posts: 557 Rating: (64)	hi (a+b)c+d/e L a L b +I L c I T z1 L d L e /R RND T z2 L z1 L z2 +I T z"final value" this logic you can develop in case of S7 300 because s7 300 is having to 2 accumulator, but in case of s7 400 you can use 4 accumulator, so you do not require z1 & z2. regards
Eastern Posts: 557 Rating: (64)
Suggestion To thank Quote Answer

5/11/2009 11:35 PM	Rate (0)
Sydney Gold Member Joined: 1/4/2008 Last visit: 3/8/2023 Posts: 703 Rating: (96)	Hello, Aret wrote that all the variables a..e are double, it means 64-bitnumber and probably meant floating point because the post is about the real numbers... Regards Sydney

Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on