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Any disadvantages to multi instance blocks

Created by: Goodas at: 7/17/2012 11:51 PM (3 Replies)

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7/17/2012 11:51 PM	Rate (0)
Goodas Posts: 37 Rating: (0)	I have written motor control blocks which incorporate selectable features, speedguard timers (SFB4) feedback timers, and full fault diagnostics. I use this as multi instance to keep programming "tidy" so one area of plant motors in one FB and as the process changes other motors into a different FB. The only external requirement is a segment to control automatic operation and interlocks. I have seen similar blocks written as FC's and then assigned a data block area (often with indirect adddressing)to store such information. Is it a case of personal preference or are there limitations to multi instances? Many thanks Goodas
Goodas Posts: 37 Rating: (0)
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7/18/2012 11:56 AM	Rate (0)
Cicero Gold Member Joined: 10/10/2005 Last visit: 1/29/2025 Posts: 1940 Rating: (138)	Hello, I can not follow your describtion. There ist a FAQ in the internet and perhaps it could be meanful for you. http://support.automation.siemens.com/WW/view/de/18723826 With best regards Cicero

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7/18/2012 12:24 PM	Rate (0)
Jazz_M Gold Member Joined: 9/6/2008 Last visit: 5/7/2022 Posts: 1121 Rating: (86)	Hi I may be right, but you have a FB that you have used a lot of times, and FC using DB as Pointer address right. Well normally it depends on the programmer to programmer. Excatly what is that you want so that we can help you. have fun...
	Jazz
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7/20/2012 4:37 AM	Rate (0)
YvonV Posts: 29 Rating: (0)	If I understand your question properly you're asking if it is better to use FB's with instance datablocks or to use FC's and assign a pointer to a DB or memory location. That is totally a programers preference. I prefer using FB's with instance DB's as I find it personally more tidy. Everything is kept together in that case. Otherwise anyone looking at the logic would have to understand the use of pointers and then identify how you are using them. but to each his own Yvon
YvonV Posts: 29 Rating: (0)
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This contribution was helpful to 1 thankful Users Goodas

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