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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: question about previous value of ai |
| From: | "Steven M. Hartman" <[email protected]> |
| To: | tech-talk <[email protected]> |
| Date: | Wed, 09 Mar 2011 09:29:04 -0500 |
Ralph Lange wrote:
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.
or . . .
record(ai,"MyAi") {
. . .
field(FLNK,"MyCalc")
}
record(calc,"MyCalc") {
field(DESC,"ai value increasing?")
field(INPA,"MyAi")
field(INPB,"MyCalc.LA")
field(CALC,"A>B")
}
--
Steven Hartman
[email protected]