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Old March 13th, 2018, 12:39 PM   #1
NetNathan
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GE RX3i - Inputs must be retentive?

Why does GE RX3i insist that the inputs (%I) be retentive?
I edited the variable declaration table for all the inputs to be non-retentive. It loaded without fault....THEN.... when I did a "Validate" it changed all of them back to Retentive??
Error on each input said that the "Memory Area Must Be Retentive changing to Retentive"??

Why would inputs have to be retentive??
Some %I references I use in my logic may not be directly connected to input module.

I guess I will have to use a first scan bit to set all my %I bits to "0"?
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Old March 13th, 2018, 01:05 PM   #2
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The only discrete memory type where you have the choice of being retentive or non-retentive is %M memory. %T memory cannot be retentive. You could use that instead of %I for those variables in your application or else just use %M and declare the variables you are concerned with as non-retentive.
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Old March 13th, 2018, 03:28 PM   #3
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Quote:
Originally Posted by Steve Bailey View Post
The only discrete memory type where you have the choice of being retentive or non-retentive is %M memory. %T memory cannot be retentive. You could use that instead of %I for those variables in your application or else just use %M and declare the variables you are concerned with as non-retentive.
The issue here is how I do my I/O mapping. all my internal plc logic is done using high %I above 200 and %Q above 200. So I map %I0001 from PLC Input module to %I201 in logic.
This allows me to do retrofits (which I do a lot of) and new logic edits quickly using the map, without having to change everywhere the bit is used in logic.
When I am troubleshooting and See a %I or %Q, I know it is related to the real world map.
Understand?
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Old March 13th, 2018, 04:06 PM   #4
Steve Bailey
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Then what is the problem with %I memory being retentive? Presumably you run your mapping routine at the beginning of the _MAIN program so you have the latest updates from the modules every program scan.
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Old March 13th, 2018, 04:21 PM   #5
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Then what is the problem with %I memory being retentive? Presumably you run your mapping routine at the beginning of the _MAIN program so you have the latest updates from the modules every program scan.
The problem is now I am doing a job that has me mapping from High to low.
I started my rack at %I0201 and am mapping down (ie...%I201 mapped to %I0001).
In my logic I may still have bits that are not mapped to (Like %I0051) and I want them to be turned off till I find them. I do not want them to come on energized...
Actually this would also exist if I mapped up. If I have not mapped %I0051, I do not want it be on.
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Old March 13th, 2018, 04:23 PM   #6
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I guess I could run a "Bit Set" (or "Bit-Clear"?) in logic to set all the %I and %Q to "0" on first scan...
Once it is done I should not really have to even run it again..
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Old March 13th, 2018, 04:26 PM   #7
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Map to a symbolic Boolean variable instead of to a %I address.
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Old March 13th, 2018, 05:01 PM   #8
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Now I have another issue see new new post on RX3i Invalid Sweep Mode?...
Found that problem..
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Old March 13th, 2018, 05:12 PM   #9
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Quote:
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Map to a symbolic Boolean variable instead of to a %I address.
How about an example of how this is done?
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Old March 13th, 2018, 05:39 PM   #10
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All of a sudden..
How come I cannot edit in logic online or offline??

Fixed that by restarting Machine Edition....weird...

This has now happened 3 times. I have to keep restarting Machine edition to edit the logic??
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Old March 13th, 2018, 06:09 PM   #11
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Here is a quick example for a single variable.
The Boolean variable named "I00018" is addressed to %I18 and is retentive.
The Boolean variable named "I00019" is not addressed (Symbolic) and has been configured a non-retentive.
The MOVE_BOOL instruction copies one to the other.
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Old March 13th, 2018, 08:19 PM   #12
NetNathan
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Quote:
Originally Posted by Steve Bailey View Post
Here is a quick example for a single variable.
The Boolean variable named "I00018" is addressed to %I18 and is retentive.
The Boolean variable named "I00019" is not addressed (Symbolic) and has been configured a non-retentive.
The MOVE_BOOL instruction copies one to the other.
Got it! That is easy enough.
So it is using memory only for addressing and not IO addresses?
And it CAN BE retentive also, you would think that because it is memory based that it is not retentive?
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Old March 14th, 2018, 08:19 AM   #13
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Quote:
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Got it! That is easy enough.
So it is using memory only for addressing and not IO addresses?
And it CAN BE retentive also, you would think that because it is memory based that it is not retentive?
Symbolic variables have no reference address, they are easy to spot in the ladder because they are displayed in a darker shade of blue. GFK-2950 has a good description on retentiveness, transitions, and overrides in section 3. Also, personally i don't like mapping registers to registers of a similar type IE %I to %I. I would map %I to %M, then execute logic with the %M register (%M can be non-retentive i think off the top of my head). Similarly to the way you would handle %AI. You'd take a raw %AI 0-32000 count value, scale it in logic into an %R, then use the %R in logic. Use the software based registers for software based stuff and leave the real IO register types free for real IO. My 2 cents
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Old March 14th, 2018, 09:26 AM   #14
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Use the software based registers for software based stuff and leave the real IO register types free for real IO. My 2 cents
I agree wholeheartedly. I prefer to avoid having an HMI access real IO altogether. There is no need for it in a well designed control system.
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Old March 14th, 2018, 10:20 AM   #15
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Like I said...
I like mapping my %I and %Q to a higher %I or %Q.
My %AI and %AQ are moved to registers, but there are only about 24 %AI and 5-8 %AQ to deal with here....but Inputs and Outputs may approach 64 inputs and 42 Outputs.
As I am troubleshooting my logic when I see a %I or %Q I know it is related to real IO. I would have to do a search to find out if the %M is related to a %I or %Q (I could shove it into the description, which makes it even longer).
I also use the mapped address, if needed, in my Intouch HMI.
Then when I do a conversion I hardly ever have to edit anything in logic.... just my mapping subroutines. No need to change core logic or HMI.
I do a lot of conversions on other pieces of equipment... made by others, so the IO is not always in the same location as equipment my company makes, especially if the PLC type changes. The vacuum furnaces I work on have almost the same operating procedure and components.
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