Indirect addressing in FB CJ2

[vasekd]

Hi all,

how can I use indirect addressing in FB for CPU CJ2. For instance in this simple example (without using D500)

 

[IO_Rack]

Since it is tag based, you'll have to use an Array instead. Edit the variable then click on Advanced.

[Crossbow]

My understanding is that if the address is prefixed with @, the actual address referenced is based on the value in that register.

So your second move command isn't writing to D500, it's looking at D500 and writing to the address indicated inside.

So based on your example code, The value 123 is written to D1500.

[vasekd]

Yes, I know it. But I need make it in FB ( It is onpy example. It will be more comlex function with start address as parameter - I will set start address on input FB and fuction use address space from it.)

[Michael Walsh]

On 11/13/2017 at 8:26 AM, IO_Rack said:

Since it is tag based, you'll have to use an Array instead. Edit the variable then click on Advanced.

I second this comment.  Use an array inside the FB with a variable as the index.  

[vasekd]

Thank you very much.

Now it's quite understandable for me .  I'll try it tomorrow.

[innoaloe]

For FB typically we use the IR and DR register for indirect addressing. Although compared to the Decimal-based reference above (The @ tag) it's more complicated to use. But pretty reliable I'd say

[Michael Walsh]

20 hours ago, innoaloe said:

For FB typically we use the IR and DR register for indirect addressing. Although compared to the Decimal-based reference above (The @ tag) it's more complicated to use. But pretty reliable I'd say

Yes, I tried to provide the simplest (although perhaps less capable) solution.  If he does not need to access memory by address specifically (as many Omron FBs require to access memory for specific modules or functions), then this is much simpler.  

[vasekd]

Thank you for the explanation. It made me learn to use IR, DR. I think it will be a good solution for my program.