Slc 5/04 Indexed Addressing

[Johnzo]

I have an automatic storage and retrieval system which uses indexed addressing to store the data for each stored and retrieved product.
This system has 10 racks which store 12 items in each rack and each item uses 14 words of data to identify it.

I need to add 2 more words of additional data but cannot find any info or logic samples to help me figure out what is going on in this programme.

I was ok using the additional 2 words at first as it appeared that words 14 & 15 were spare throughout the many COPy's as the product goes through its processes's, but in a manual or maintenance mode the following statement is used and I don't know what it means as far as where the data goes, how it is pointed etc.

Can anyone help me with this?

COPy #N190:40 to #N[N16:10]:[N16:11] Len14

And the reverse at retrieval

COPy #N[N16:10]:[N16:11] to #N190:40 Len14

Thanks in advance for any help ; )

 

[sthompson]

COPy #N190:40 to #N[N16:10]:[N16:11] Len14

And the reverse at retrieval

COPy #N[N16:10]:[N16:11] to #N190:40 Len14

N16:10 points to the File Number to Copy To/From
N16:11 points to the first Element to Copy To/From

Presumably, if you change the length of the COP Instruction to Len 16, it should work, but without seeing the PLC Code, we can only guess.

If you Right Click on an empty spot in the Ladder Logic, select Properties, the the Address Display Tab, there is a Check Box towards the bottom "Display Value for Indirect Address" that may help you understand what is going on.

Stu.....

 

[Johnzo]

Thanks Stu,

I did what you said and now see a value of 212 for #N16:10 and 0 for #N16:11.

Does this mean that 212 = N212 starting at 0 for a length of 15 (my mistake, the length is 15 not 14, which negates using the last 2 words)?

My next question is by what mechanism does N212 become involved in this. Where in the logic is N212 called into play?

 

[sthompson]

Yes, in this case the COP Instruction will move the 15 Words starting at N212:0 To/From N19:40.

It is hard to answer your specific question without seeing the PLC Code. If you search for N16:10/N16:11, you should find some more PLC Code that moves the Value into it based on some criteria. i.e. Product Selection 1,2,3.....X

Stu....

 

[Johnzo]

Ok, I now see that N212 is a variable word number representing a physical storage location, this makes sense now.

In other threads I have read about S:24 playing a role with indexed addressing, is this the case and if so, how?

Thanks again for the help Stu!

 

[sthompson]

I should have paid more attention. What you have in your PLC is Indirect Addressing, not Indexed Addressing. S:24 is used for Indexed Addressing, but not Indirect Addressing.

You might want to have a look at the SLC500 Instruction Reference to understand the difference. You can get it here;

http://www.rockwellautomation.com/global/literature-library/overview.page

Search for 1747-RM001E, and if that doesn't work, try searching for "SLC500 Instruction Reference".

Stu....

 

[Johnzo]

I thought if it had a "#" it was indexed addressing?

Looking at the file you sent it may be indexed indirect addressing!

I think I can muddle my way through this now, thanks again Stu, big help, have a great weekend!

 

[sthompson]

The # indicates a File Instruction. The PLC does use the Index Register during the Execution of the Instruction.

Have a look at Page E-15 of the Instruction Reference Manual.

Stu....