You are not registered yet. Please click here to register!


 
 
plc storereviewsdownloads
This board is for PLC Related Q&A ONLY. Please DON'T use it for advertising, etc.
 
Try our online PLC Simulator- FREE.  Click here now to try it.

---------->>>>>Get FREE PLC Programming Tips

New Here? Please read this important info!!!


Go Back   PLCS.net - Interactive Q & A > PLCS.net - Interactive Q & A > LIVE PLC Questions And Answers

PLC training tools sale

Reply
 
Thread Tools Display Modes
Old September 10th, 2019, 07:49 AM   #1
FreeAtLast
Supporting Member
United States

FreeAtLast is offline
 
Join Date: Mar 2019
Location: Nashville
Posts: 10
Does AOI execution complete before scan continues?

Hi all.
I have a conceptual question about how program execution happens around AOIs in Studio 5000 V31 or V32. When the processor's scan comes to an AOI, say on rung 15, does the execution enter the AOI and wait to move to rung 16 until it has scanned all the rungs inside the AOI?

Or, alternatively, does execution enter the AOI on rung 15, and then immediately continue to rung 16 causing a kind of parallel execution where logic can be executed in two places at once.

Thanks for your input!
  Reply With Quote
Old September 10th, 2019, 10:19 AM   #2
Aabeck
Member
United States

Aabeck is online now
 
Aabeck's Avatar
 
Join Date: Feb 2013
Location: Detroit
Posts: 1,372
I haven't read anything official on this, but I would say it executes the AOi completely before continuing the calling routine.
I say this because the next rung can get the result of the output parameters, which if done concurrently wouldn't be available yet.
__________________
Never underestimate the quality of idiots that will be running your machines
http://aabeck.com
  Reply With Quote
Old September 10th, 2019, 10:31 AM   #3
Ron Beaufort
Lifetime Supporting Member
United States

Ron Beaufort is offline
 
Ron Beaufort's Avatar
 
Join Date: Jul 2002
Location: Charleston, SC
Posts: 5,540
even going beyond your concerns about Add On Instructions - there are some potential "gotchas" involved in the asynchronous scan sequences of the "Logix" family systems ...

this post - and the following discussion might be interesting to you ...

http://www.plctalk.net/qanda/showthr...7&postcount=61

.
__________________

2-B ?
Best regards, ----+----] [----+------------( )----
Ron | |
PLC Training Boot Camp - Retired | 2-B |
+----]/[----+

I once was lost, but now am found, was blind, but now I see.


Last edited by Ron Beaufort; September 10th, 2019 at 10:50 AM.
  Reply With Quote
Old September 10th, 2019, 02:05 PM   #4
scameron81
Member
United States

scameron81 is offline
 
Join Date: Jun 2011
Location: Northern California
Posts: 41
I can tell you that it will stop scanning mid AOI if a periodic task gets called. I had a glitch that took me a long time to figure out because of a periodic data transfer task that would interrupt the AOI every so often and then send bad data to the other PLC’s because the AOI hadn’t finished processing. Since then I have learned to truly encapsulate my AOI’s
  Reply With Quote
Old September 10th, 2019, 02:38 PM   #5
bernie_carlton
Lifetime Supporting Member + Moderator
United States

bernie_carlton is offline
 
bernie_carlton's Avatar
 
Join Date: Apr 2002
Location: Yakima, Washington
Posts: 6,297
Scameron81 - could you expand on the procedures you used to 'encapsulate' your AOIs?
__________________
Controlling outputs is the PLC's way of getting its inputs to change.

www.thePLCguy.com
  Reply With Quote
Old September 10th, 2019, 05:00 PM   #6
RET
Member
United States

RET is offline
 
Join Date: Feb 2015
Location: Houston, TX
Posts: 232
Quote:
Originally Posted by scameron81 View Post
I can tell you that it will stop scanning mid AOI if a periodic task gets called. I had a glitch that took me a long time to figure out because of a periodic data transfer task that would interrupt the AOI every so often and then send bad data to the other PLCís because the AOI hadnít finished processing. Since then I have learned to truly encapsulate my AOIís
I'd like to know exactly what you mean by "truly encapulate my AOI's"....by design they're already self-contained routines.
__________________
This statement is false.
  Reply With Quote
Old September 10th, 2019, 05:59 PM   #7
kamenges
Member
United States

kamenges is offline
 
kamenges's Avatar
 
Join Date: Nov 2002
Location: Brillion, WI
Posts: 3,874
If I had to take a guess he is using UID/UIE pairs to disable interrupts when his AOI is running. Or he is using a CPS before and after to freeze his data, depending on the issue he was having.

Keith
  Reply With Quote
Old September 10th, 2019, 10:42 PM   #8
bernie_carlton
Lifetime Supporting Member + Moderator
United States

bernie_carlton is offline
 
bernie_carlton's Avatar
 
Join Date: Apr 2002
Location: Yakima, Washington
Posts: 6,297
Since we are guessing I think maybe setting an 'in AOI' flag at the beginning and resetting it at the end. The bit would be tested by the periodic task.
__________________
Controlling outputs is the PLC's way of getting its inputs to change.

www.thePLCguy.com
  Reply With Quote
Old September 11th, 2019, 11:10 AM   #9
daba
Lifetime Supporting Member + Moderator
United Kingdom

daba is offline
 
daba's Avatar
 
Join Date: Jul 2004
Location: uk
Posts: 4,587
It matters not whether it is an AOI, a routine, or another interrupting task. The logic is scanned in sequential order, so any concerns about your data being "half finished" would apply in all cases.

Make your data transfers use "buffered" data only, so you know it will be a complete "data-set". Use CPS to populate it, since COP can be interrupted also.
__________________
___________________________
ControlLogix & SLC Training
a-b train ltd.
abtrain@tiscali.co.uk
www.abtrain.co.uk
tel: 07506 73 9999
nil illegitimi carborundem


  Reply With Quote
Reply
Jump to Live PLC Question and Answer Forum

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Topics
Thread Thread Starter Forum Replies Last Post
AB PLC5 PIDs Derek McFarland LIVE PLC Questions And Answers 23 March 2nd, 2005 01:18 AM
S7 prgram scan Rack Failure LIVE PLC Questions And Answers 9 February 5th, 2005 10:12 AM
AB PLC5 Scan Time Question pnally LIVE PLC Questions And Answers 3 February 14th, 2004 05:04 PM
RSView 32 problem vufu LIVE PLC Questions And Answers 4 July 10th, 2003 01:10 PM
Compare register from one scan to another scan lostpatrol1 LIVE PLC Questions And Answers 7 April 22nd, 2003 12:29 PM


All times are GMT -5. The time now is 01:20 AM.


.