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<== Date ==> <== Thread ==>

Subject: Re: question about previous value of ai
From: Ralph Lange <Ralph.Lange@gmx.de>
To: tech-talk <tech-talk@aps.anl.gov>
Date: Wed, 09 Mar 2011 10:47:57 +0100
On 09.03.2011 08:55 Silver wrote:
   I use an ai record to retrive the value from hardware, in my SNL program, I want to compare the previous value of ai and the new value, then do some action.
   how can I get the previous of ai?

Either - in the SNL program - by assigning the current value to a local variable as part of your action.

Or - in the database - by adding another ai record that pulls the old value from your hardware-ai before processing it via FLNK. (Won't work for I/O scanned hardware ai.)

Or - in the database - by adding a compress record that is configured as a ring buffer, which can hold the arbitrary length history of an ai.

Hope this helps,
~Ralph

Replies:
Re: question about previous value of ai Steven M. Hartman
References:
question about previous value of ai Silver

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