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S7-1200 positive edge detection

Created by: ionut.b at: 11/10/2011 10:50 AM (9 Replies)

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11/10/2011 10:50 AM	Rate (0)
ionut.b Bronze Member Joined: 1/17/2007 Last visit: 10/6/2020 Posts: 289 Rating: (3)	Hello, Compared to S7-200 where a positive edge detection was active for only one scan, at s7-1200 the instruction is active as long as the trigger bit is on; it does not reset at next scan. How to reset it even if the trigger bit is still on? Thank you.
	Last edited by: ionut.b at: 11/10/2011 12:48 PM
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11/10/2011 12:47 PM	Rate (0)
ionut.b Bronze Member Joined: 1/17/2007 Last visit: 10/6/2020 Posts: 289 Rating: (3)	Looking into S7-1200 system manual at 7.1.3 it explains all positive/negative edge instructions. At all three types doesn't mention about "ON" state for only one cycle. But if I look in TIA PORTAL V11 help, at --(P)--:Set operand on positive signal egde it does mention about "ON" state for one program cycle. Still in my test this instruction is "ON" allways, not just on one program cycle.

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11/10/2011 12:59 PM	Rate (7)
William_B Posts: 5225 Rating: (1198)	ionut.b Compared to S7-200 where a positive edge detection was active for only one scan, at s7-1200 the instruction is active as log as the trigger bit is on; it does not reset at next scan. Hi! The S7-200 spoilt us with the way the positive/nagative edge trigger works. In actual fact there are a couple of memory bits associated with each edge trigger you use. Those memory bits you never see. I am not sure on the number but I think it there are 256 edge trigger bits. so you can use a maximum of so many edge triggers in your S7-200 program. Back to the S7-1200.. There you have to tell the software which memory bit should be used to remember that the variable has triggered. See the JPG attached. Both have the same influence for all M0.x bits. M11.x is the remember-the-edge memory and is used only once. M11.x is used nowhere else in your program M11.x can also be a bit from a DB, but never from a "local" variable. M0.0 is an edge triggerd output because of everything before it. M0.1 -- only the edge of I0.0 is counted. M0.2 is how you used it in the S7-200 >> remember [P_Trig block & M11.3] together is the edge trigger you used and loved in the S7-200. okay? okay! Please tell me if this text helped. Attachment edge trigger methods.jpg (8148 Downloads)
William_B Posts: 5225 Rating: (1198)
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11/11/2011 12:54 PM	Rate (0)
ionut.b Bronze Member Joined: 1/17/2007 Last visit: 10/6/2020 Posts: 289 Rating: (3)	Hello William B. Thank you for the reply; I found what I was looking for in your examples. Best regards.

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11/11/2011 2:17 PM	Rate (0)
William_B Posts: 5225 Rating: (1198)	Glad to have been of service to you.
William_B Posts: 5225 Rating: (1198)
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12/26/2012 7:51 PM	Rate (0)
kidsolo1412 Regular Member Joined: 4/24/2010 Last visit: 1/12/2025 Posts: 16 Rating: (0)	P_TRIG not exactly same as P in S7-200.I try like below: I0.0---(P_TRIG)----Set Q0.0 (I0.0 is my sensor) If my sensor hasalready been on then when i turn on the PLC, Q0.0 will be set In S7-200,Q0.0 will not be set until my sensor is off and turn on again

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11/24/2013 1:42 AM	Rate (0)
cdraughter Posts: 2 Rating: (0)	Hello, Thanks for your post. I am new to S7 1200 and Siemens. I am not understanding how to reset this if its only going to remember the last state. Am I thinking of this correctly? Thanks for all your insight. Charlie
cdraughter Posts: 2 Rating: (0)
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11/25/2013 7:00 PM	Rate (0)
0_Einstein Diamond Expert Joined: 7/7/2010 Last visit: 1/24/2025 Posts: 15558 Rating: (2468)	cdraughter Hello, Thanks for your post. I am new to S7 1200 and Siemens. I am not understanding how to reset this if its only going to remember the last state. Am I thinking of this correctly? Thanks for all your insight. Charlie If you are making a toggle, you look to see a bit is on, then p_trig the input to (r) reset the bit.
	science guy
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12/6/2016 3:59 PM	Rate (0)
surefire Member Joined: 11/21/2016 Last visit: 6/23/2022 Posts: 3 Rating: (0)	Thanks it is very helpful

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5/30/2022 10:36 PM	Rate (0)
PrograMex Member Joined: 5/14/2021 Last visit: 11/9/2022 Posts: 3 Rating: (0)	Tnks for the examples!

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