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INTERUPT help -s7 1200

Created by: vipz at: 2/23/2014 8:49 AM (6 Replies)

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2/23/2014 8:49 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 9/25/2025 Posts: 712 Rating: (30)	Hai all, Recently i have attended one site where S7 1200, S 120, G120 drives are used. this is related with packing machine. the programmer used following blocks -- 1. Cyclic interupt OB (each 15ms ) - 1 number Here based on servo position, need to make around 50 outputs high (servo is configured 0-5000 LU, whic coresponds to 0-180 Degree. Each output is indipendent, ie 1st may get on at 150 deg, 2nd at 170 deg etc and this setpoin is from hmi). 2. Cyclic interupt OB ( Each 8ms) - 1 number Here read and write values to the drives(setpoits, start n stop commands etc) Both the cyclic interupt OBs are of priority 7. 3. Hardware interupt OB ( 4 numbers for 4 digital input) - 4 numbers here some drive's stop command is configured. When this sensor is high, corresponding drive should stop the motor.( drive-plc communication is in profinet for G120, profibus with 6mb/s for s120). Here problem facing is a. in the case of 1. Cyclic interupt OB (each 15ms ) logic, some times digital outputs are missing. In drive trace function, we can see that LU is reaching at required setpoint, but plc is not generating Output. b. in the case of 3. Hardware interupt OB ( 4 numbers for 4 digital input) drive is not stopping immediately. (sometimes this problem happening) So i think some thing is problem because of scan issue. Also please clariffy me about scan sequence and output writing. A. if cyclic interupt OB of 15ms is running, then cyclic interupt OB of 8 ms condition reached. then what will happen ? B. if if cyclic interupt OB of 15ms Or OB of 8 ms is running, then hardware interupt came. what will happen ? C. As per the condition, digital output will be writting in each scan cycle or immediately after the execution of Cyclic interupt OB ? D. In the case of drive start - stop command (reseting of "start command" is written in hardware interupt ob, writting to drive pqw is written in cyclic interupt ob of 8ms ). When will be the command going to drive ? total scan time of cpu is showing 40-80 ms.
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2/24/2014 6:50 AM	Rate (1)
Raednabeel Posts: 96 Rating: (7)	As I know: Outpus will be written after a complete cycle of the cyclic OB1, So in case OB1 at the middle and it has been interupted by a cyclic interupt or event interupt, CPU will terminate OB1 and execute that interupt then it will return to OB1 and continues from where OB1 was termintaed. so the values of the outputs will be determined by the last executed insturction, just before the end of OB1. on the other hand, to make sure each cycle interupt is being fully executed, use "Phase offset" ------------------------------Extracted of TIA Portal V11 Help ------------------------------ Example of the use of phase offset You have inserted two cyclic interrupt OBs in your program: Cyclic interrupt OB1 Cyclic interrupt OB2 For cyclic interrupt OB1, you have set a time base of 20 ms and for cyclic interrupt OB2 a time base of 100 ms. After the expiry of the time base of 100 ms, the cyclic interrupt OB1 reaches the start time for the fifth time, cyclic interrupt OB2 for the first time. To nevertheless execute the cyclic interrupt OBs offset, enter a phase offset for one of the two cyclic interrupt OBs. ----------------------------------------------------------------
Raednabeel Posts: 96 Rating: (7)	Last edited by: Raednabeel at: 2/24/2014 6:52 AM
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2/24/2014 8:36 AM	Rate (0)
vipz Gold Member Joined: 9/2/2012 Last visit: 9/25/2025 Posts: 712 Rating: (30)	Hai, Now am talking about 15ms cyclic interupt OB.(say OB2) If my OB is satisfied for generating DIGITAL OUTPUT during 1st call, immediately it will not write into the digital output since my OB1 scan is around 70ms. So before finishing the OB1 scan, OB2 will get called again. Say during this scan Digital Output condition is not satisfied in OB2, after that OB1 finishing the full scan cycle. This case i will miss digital output, correct ??
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2/24/2014 2:33 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/23/2025 Posts: 16325 Rating: (2520)	vipz Hai, Now am talking about 15ms cyclic interupt OB.(say OB2) If my OB is satisfied for generating DIGITAL OUTPUT during 1st call, immediately it will not write into the digital output since my OB1 scan is around 70ms. So before finishing the OB1 scan, OB2 will get called again. Say during this scan Digital Output condition is not satisfied in OB2, after that OB1 finishing the full scan cycle. This case i will miss digital output, correct ?? If your cyclic OB directly acts on the output rather than the output image by using Q0.0:P rather than Q0.0, the output should change state immediately. There may be plenty of unnecessary plc code being solved to have such a high scan time. I've programming packaging and packing equipment in the past, and I have to wonder 1) why they chose the s7-1200 if the best they can achieve is 70 ms scan times, and 2) what kind of data manipulation they are doing every scan. Are they packing peanuts into a nice matrix with a camera input? (I'm kidding as that would probably push it beyond the s7-1200's current capabilities unless all the smarts is offloaded to an intelligent camera and servo/smart drive).
	science guy
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2/24/2014 3:08 PM	Rate (0)
Raednabeel Posts: 96 Rating: (7)	Try to check if there are multibile logic ( i.e. program networks ) write on same output
Raednabeel Posts: 96 Rating: (7)
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2/24/2014 5:45 PM	Rate (1)
vipz Gold Member Joined: 9/2/2012 Last visit: 9/25/2025 Posts: 712 Rating: (30)	Hai Huggy you mean to say if using Q0.0:P addressing, it will write immmediately ?? (like peripheral adresing in s7 300) -- its a tea powder packing application. HaiRaednabeel, no, outputs are used only once in program.
	With Best Regards VIPZ
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2/24/2014 6:11 PM	Rate (0)
0_Einstein Grandmaster-Expert Joined: 7/7/2010 Last visit: 12/23/2025 Posts: 16325 Rating: (2520)	vipz Hai Huggy you mean to say if using Q0.0:P addressing, it will write immmediately ?? (like peripheral adresing in s7 300) -- its a tea powder packing application. HaiRaednabeel, no, outputs are used only once in program. Yes, immediately.
	science guy
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