Shifting an Array Of Dints

[kevilay]

Hey guys,

What do you suggest for doing a shift of dints within an array like this?

Thanks,
Kevin

 

[drbitboy]

FFL and FFU instructions do that.


I don't know if they work with DINTs though.

 

[kevilay]

FFL and FFU instructions do that.


I don't know if they work with DINTs though.

Okay. I will read through the instruction help to see. The move instruction is nice and simple but Im looking to expand the number of results considerably.

 

[drbitboy]

see here

 

[kevilay]

FFL and FFU instructions do that.


I don't know if they work with DINTs though.

Oh I guess I could just use a copy instruction with a length minus 1

 

[nmurray]

If you don't mind going in reverse order I'm pretty sure the COP instruction works

[cop]
[SOURCE: Station30CycleHistory[1] ]
[DEST: Station30CycleHistory[0] ]
[LENGTH: 10 ]

 

[drbitboy]

Oh I guess I could just use a copy instruction with a length minus 1

Those instructions do work with DINTs.

 

[GaryS]

This will work
it moves the values up in the array
the problem with file copies is they start a index 0 and copy it to index 1
and 1 is copied to 2
starting at 0 over weighting the data before it's moved
the way I show starts at the top and indexes down
I have tested it with arrays of over 1000 and with used defined data types

 

[Jim3846]

There is actually 2 different ways to shift DINT in a file.

Input trigger is some pulse.

Shift from Bottom of file to top, only need 1 copy statement
You would mov whatever number into the last word, then as you execute the copy statement, the value would move 1 spot up in file.

Shift from Top of file to bottom, you need 2 copy statement.
Mov a value into first word.

 

[kevilay]

There is actually 2 different ways to shift DINT in a file.

Input trigger is some pulse.

Shift from Bottom of file to top, only need 1 copy statement
You would mov whatever number into the last word, then as you execute the copy statement, the value would move 1 spot up in file.

Shift from Top of file to bottom, you need 2 copy statement.
Mov a value into first word.

I didn't realize how the copy instruction worked exactly. This makes alot of sense. Thanks for your help.

 

[plvlce]

Shift from Top of file to bottom, you need 2 copy statement.

You also need twice as much memory to do it this way...

 

[drbitboy]

It can also be done with indices and a "circular" DINT array buffer.


The tradeoff is more efficient processing vs. more (and messier) code.


How big is the array?

 

[kevilay]

The length of the array is subjective. I am going to start with 100. It is a cycle time history. I think it will be very confusing to our customer if it was backwards. So I will do the array with the two copies. I also changed things a little bit so I could use a SINT instead of a dint.