What is the significance of SubIndex when CA is TRUE?

[ShabbyX]

In ecx_SDOread() and ecxSDOwrite(), the parameter CA says:

FALSE = single subindex. TRUE = Complete Access, all subindexes read/written.

And the parameter SubIndex says:

Subindex to read, must be 0 or 1 if CA is used

What is the difference between 0 and 1 if CA is used?

[mheden]

I think it has to do if you want to write the "Number of elements" (subindex 0) item or not together with your data or not.

In a lot of slaves the subindex 0 is not writable (or only writable in certain states) so I assume this adds the possibility to do a complete access writes for such slaves. It could also be useful if you want to read/write a whole struct without adding the number of elements item to the struct.

[ShabbyX]

Thanks, that makes sense. I think our slave doesn't have a special "Number of Elements" at subindex 0, so it would make sense for me to read the whole thing as a struct.