fifo help in rslogix 500 please

sorry about that I was type on my phone (all fingers and thumbs),
I thought that's what I would need to do, so when the fifo hit's 5 it will reset back to 0 and start again ?
I hope that makes sense all the best stu
 
sorry about that I was type on my phone (all fingers and thumbs),
I thought that's what I would need to do, so when the fifo hit's 5 it will reset back to 0 and start again ?
I hope that makes sense all the best stu

No. When the FIFO hits 5 and is full what happens is that no more data can be entered. Unload one value and one can be entered. It won't 'empty' 'til you execute five FFUs.
 
I think I am following the thread now. Bernie gave you a sample which you are trying to use as a guide. On the first rung branch, if first does a FFU, only if R6:0/DN is ON, just to make sure that is at least one clear space in the FIFO stack.

Then on the next rung branch, you are supposed to set your Source word for the following FFL. You must do this BEFORE you do the FFL, not after as you have it now. Bernie did a dummy word by adding 1 to N7:0 and saving it back to N7:0. For your program, you need to bring in the newest Water Weight (from F34:0 ?) and save it in N7:1. (If the Water Weight has 2 decimal places, first multiply it by 100 so that when you put it in N7:1, xxx.yy will become xxxyy).
 
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Here are changes that allow loading 10 values into the 2 FIFO memory stacks. With this arrangement, I think that you could delete the ONS one-shot bit.
 
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Hi Lancie1
Thanks for that I will give it ago over the weekend but I appreciate your help thanks ,stu
 
Hi Lancie1
Thanks for your help , I have another question with the unload when the position value reaches the source value ie 10 is the unload ment to reset or does it just unload one at a time ,i'm going to have a look tonight anyway , thanks again stu
 
Hi Lancie1
Thanks for your help , I have another question with the unload when the position value reaches the source value ie 10 is the unload ment to reset or does it just unload one at a time?
Well, FFL and FFU always do one Position at a time (1 per PLC scan). Whether they do more the next PLC cycle depends on your enabling trigger and other logic.

When R6:0.POS = R6:0.LEN, then the operation is Done and the R6:0/DN bits goes ON.
 

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