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HSC multiple presets (again)

Created by: Mark_F at: 1/4/2013 2:39 PM (14 Replies)

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1/4/2013 2:39 PM	Rate (0)
Mark_F Experienced Member Joined: 8/22/2011 Last visit: 9/30/2024 Posts: 47 Rating: (1)	Hi to everybody reading this. It's me again with questions about HSC in S7-1200. I'm trying to make a program with 2 presets. First preset (let's say 1000 counts) is loaded in I0.0 rising edgehardware interrupt. When the counter reaches preset value, CV=PV hardware interrupt routine occurs and loads the next preset value (1500 for example). Now when the next preset is reached I'd like to reset the counter by setting CV to 0. What bothers me is that the reset should be conducted in the same CV=PV interrupt routine and I cannot get the program not to reset the value after first CV=PV. How do you guys write your multiple presets programs? Would you pleasebother to have a look at the example attached. Best Regards Attachment Project2.zip (571 Downloads)

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1/4/2013 4:25 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	You add a step variable. When the interrupt triggers you look at your step variable and set appropiate set value - this should be ASAP for not loosing pulses when its in int. routine. Then you increment step=step+1.

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This contribution was helpful to 1 thankful Users Mark_F

1/4/2013 4:57 PM	Rate (0)
Mark_F Experienced Member Joined: 8/22/2011 Last visit: 9/30/2024 Posts: 47 Rating: (1)	Thank you, imenjače :D I just thought of increment instruction few minutes ago. So one Inc MB20 (SInt) is in rising edge interrupt and another in CV=PV interrupt. When MB20=1 CV=PV interrupt sets the new PV; when MB=2 CV=PV will reset the value.
	Last edited by: Mark_F at: 1/4/2013 4:58 PM
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1/5/2013 1:20 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	Yes, you could also use bool type of variable. If you are changing counter value, then you should set it as fast as possible once in interrupt routine. If you change the preset value than this has no such importance. Anyway the compare function is slower than checking boolean variable, so you can use also set/reset bit. The basic rule is: 1st check your flag variable (bit or int, ...) then write to counter, only then change flag variable, it is the fastest response of program to counter change.

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1/5/2013 7:00 PM	Rate (0)
Mark_F Experienced Member Joined: 8/22/2011 Last visit: 9/30/2024 Posts: 47 Rating: (1)	Marko Bursic Yes, you could also use bool type of variable. If you are changing counter value, then you should set it as fast as possible once in interrupt routine. If you change the preset value than this has no such importance. Anyway the compare function is slower than checking boolean variable, so you can use also set/reset bit. The basic rule is: 1st check your flag variable (bit or int, ...) then write to counter, only then change flag variable, it is the fastest response of program to counter change. The problem with set/reset is that bit is set within the same interrupt routine in which it is checked. So CV=PV sets the bit which is a condition for reset and immeditely resets the counter. I've also tried to set bit within an FC which is called by interrupt - same thing. So I put compare instruction outside of interrupt routine and they energize the neccesary bits.

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1/9/2013 12:54 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	I don't fully understand your situation, but I would reset the counter in interrupt routine and also control the logic. If it is too complicated then, ok. It also depends on the accuracy of your application. If the counter reaches presset value CV=CP then triggers interrupt, if you reset the counter outside intr. routine then the counter will continue to count until your program will reach the clear command and those pulses are lost. dali ti je jasno?

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1/9/2013 1:23 PM	Rate (0)
Mark_F Experienced Member Joined: 8/22/2011 Last visit: 9/30/2024 Posts: 47 Rating: (1)	Somewhat jasno. I understand that I'll lose pulses if I reset counter outside of interrupt. Please see attached project. If I set M12.3 whitin interrupt, HSC will reset immediately. I've solved the problemthis way and I believe there are million other ways to do it. Thanks for helping btw
	Last edited by: Mark_F at: 1/9/2013 2:05 PM attachment deleted Last edited by: Mark_F at: 1/9/2013 1:24 PM Last edited by: Mark_F at: 1/9/2013 1:23 PM
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1/9/2013 1:39 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	Sorry, I don't download projects. You can post a screenshoot if you want. As you said there are many ways to go, and if you solved the problem then its ok. I gave you just a pre-warning in case your application needs very accurate counting like moving forward and backward without loosing pulses, I suppose you don't have it as you are reseting the counter so each time you have a new start position.

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1/9/2013 2:09 PM	Rate (0)
Mark_F Experienced Member Joined: 8/22/2011 Last visit: 9/30/2024 Posts: 47 Rating: (1)	Here are the screnshots if you (or others) areinterested. So first CV=PV --> new PV is loaded; second CV=PV --> HSC reset. Bits M12.x for steps are energized externally in the Main OB. Attachment captures.zip (524 Downloads)

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1/10/2013 1:13 PM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	I would made it more simple. In intr. routine call FC1(HSC) and give this parameters: network1: Set_PV=MB20.0 Set_CV=MB20.1 New_PV=1500 New_CV=0 nework2: (i will write it in STL, I hope you will understand) A MB20.0 R MB20.0 S MB20.1 RET network3: A MB20.1 R MB20.1 S MB20.0 Et voila, you can now set your step(MB20) variable also outside intr. routine. I don't preffer using flank functions in intr. as you did (P output). Please make sure you have a RET (return, quit from interrupt) in network 2. It might be also better, to use a call to counter directly, not by using FC1 - each nesting call uses time. I put a call to counter in first network, ASAP. Now I suppose for first time you are using one another inetrrupt that triggers on I0.0. You may have to disable interrupt when accesing counter function in order to prevent a double call from other interrupt routine (see priority levels) . Its also importand that you never use counter function in OB1 for same reason, or maybe you can disable intr. first, call function in ob1 and then enable intr. again. what is also strange, what will your application do when you set CV=0, the next interrupt will occur when CV=1500, so you didn't make a big deal. Explain exactly the whole cylcle, from begining.
	Last edited by: Marko Bursic at: 1/10/2013 1:35 PM Last edited by: Marko Bursic at: 1/10/2013 1:21 PM
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This contribution was helpful to 1 thankful Users Mark_F

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