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TIA PORTAL V13 UPD 4, LOOP instruction

Created by: Razvansql at: 5/4/2015 2:18 PM (5 Replies)

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5/4/2015 2:18 PM	Rate (0)
Razvansql Advanced Member Joined: 4/9/2013 Last visit: 11/21/2024 Posts: 26 Rating: (0)	Hi, I'm using TIA PORTAL V13 UPD 4. I saw that there is a LOOP instruction, in the "Basic Instructions" section. I've read the help content but i find it hard to understand. Can someone make a simple exemple using this instruction? ---------------------------------------------------------------------------------------------------- Split from Loop.
	Last edited by: Min_Moderator at: 5/4/2015 2:48:59 PM
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5/4/2015 2:44 PM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Razvansql Hi, I'm using TIA PORTAL V13 UPD 4. I saw that there is a LOOP instruction, in the "Basic Instructions" section. I've read the help content but i find it hard to understand. Can someone make a simple exemple using this instruction? * Which PLC? ...... I am guessing : S7-300 * Which program language? ...... I am guessing : STL
William_B Posts: 5225 Rating: (1197)
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5/4/2015 4:23 PM	Rate (0)
Razvansql Advanced Member Joined: 4/9/2013 Last visit: 11/21/2024 Posts: 26 Rating: (0)	Sorry, i forgot... Yes, i'm using STL language on a S7-300. :)

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5/4/2015 5:02 PM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Razvansql Sorry, i forgot... Yes, i'm using STL language on a S7-300. :) The LOOP instruction tripped me over the first time too. In the HELP you see the example: L <number> <jump label>: T <loop counter> ... Any program L <loop counter> LOOP <jump label> After filling in some values it may look like... // S A M P L E 1 //------------------------------ L 20 // example: repeated x20 NXT1: // Loop back to this label x20 times T MW30 // MW30 is the loop counter! Example only. //... Any program L MW30 // Repeat the loop counter. LOOP NXT1 T MW30 // (not required) This value is always zero. Something you have to remember about LOOP is that is a group of instructions, such as: L 1 -I // subtract 1 from the value.. // ..in the accumulator JP NXT1 // if the result is bigger than 0.. //..then jump back It is required to load the loop counter (L MW30) before LOOP instruction is called and to have a write back to loop counter (T MW30) when the instruction loops back. The LOOP instruction will decrease the loop counter at each iteration. Then the decreased loop counter will be compared to be above zero. If the result is above zero, a jump back to label will occur. If the result is zero or less, the program continues. Please do be careful on how many iterations are done. Many watchdog-timer overruns are because of this cause. The watchdog overrun puts the PLC into stop as the scan cycle is then too long. Please have a look at the other example in the HELP. Does it all make more sense now? w
William_B Posts: 5225 Rating: (1197)	Last edited by: William_B at: 5/4/2015 5:15:57 PM finish text Last edited by: William_B at: 5/5/2015 9:19:00 AM compensate for minor format error of commentary in code block
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This contribution was helpful to 1 thankful Users Razvansql

5/5/2015 8:43 AM	Rate (0)
Razvansql Advanced Member Joined: 4/9/2013 Last visit: 11/21/2024 Posts: 26 Rating: (0)	Thanks for the answer. It was really helpful.

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This contribution was helpful to 1 thankful Users William_B

5/5/2015 9:24 AM	Rate (0)
William_B Posts: 5225 Rating: (1197)	Razvansql Thanks for the answer. It was really helpful. sort of off-topic.. (1) Now that you are programming the S7-300 in TIA - consider using SCL. The SCL language do have a FOR-loop to work with. There are some other good things about it too - like the "AT overlay". (2) Consider upgrading your version of software. I am running TIA Poratal V13 SP0 Update6 and is "happy" with it. (wink) ..but maybe finish your current project first. w
William_B Posts: 5225 Rating: (1197)
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