Jump to content
klijo

V570 Immediate read physical input

Recommended Posts

The response time should be the same as the response time of the input.

 

The main variation would come from the program scan time as the immediate read would update the value mid scan instead of waiting until the next scan cycle to update.

 

If your scan time is 20ms and your input updates 1 ms into that, after inputs are normally read, it would be 21 ms before the value changes (assuming logic doesn't affect it). 

 

With the immediate function all logic following after the update portion would use the new value, maybe just a few ms to update from the immediate read.   This could cause some interesting logic bugs though, with one rung using a different value than another rung than intended due to the update.

Share this post


Link to post
Share on other sites

Put the immediate read and whatever logic you immediately care about in an interrupt routine.  If you use a 1.25 ms routine, your response time is 2.5 ms (the input has to be off for one scan).

 

This is only good for inputs directly attached to the PLC, not expansion I/O.

 

Joe T.

Share this post


Link to post
Share on other sites

Certain inputs can configured as High-Speed Counters that will count and/or measure frequency. Check the Help file and examples included with VisiLogic for more detail.

Share this post


Link to post
Share on other sites

I have the following situation in attachments:

For such application you actually require a hardware input interrupt subroutine, This type of subroutine trigers on every rising or falling edge of the input.  In unitronics we don't have such subroutine. You can use a read immediate input function but action will be taken as per scan time of PLC. Minimum time will be 1.25mS. 2nd profile is posible because the speed is very slow before stoping, But in 1st profile there may be some errors as speed is very high and it may miss the stop plus because it will be scaned every 1.25 mS. I had tried using a V130-J-TR20 for labeling application but i had problems while stoping plus.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...