Struct problem

DonWare · Joined: 18 Jan 2006 Posts: 43

Hi, I'm having trouble defining a struct. The code below compiles OK but complains about subscript range errors if I increase the numbers to ~10 or more. I'm using a PIC16F877.

struct setup{
int8 pname[5];
int8 seq_cnt;
int8 sname[5];
int8 sdata[5];
}MyData[5];

I didn't do the math but is it really just purely an 'out of memory' problem ?

Also, hows does using a 'union' differ. I can't find much into on it within CCS.

Thanks. Don

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

In a 16F877, the largest available block of user RAM within a single RAM
bank is 96 bytes. A structure must contained within one RAM bank.
It can't span two or more banks. That's the reason for the error message.
To remove this limitation, use an 18F PIC with the PCH compiler.

DonWare · Joined: 18 Jan 2006 Posts: 43

OK thanks. That example I gave only totaled 80 bytes (I think). But I'll keep it in mind.

Don

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Right, but you said the problem was not with the posted structure, but
rather with another one (not shown) that had the array size(s) increased
to 10. If you still have a problem, post the structure that is causing the
error.

ferdem · Guest

Ttelmah · Guest

Just define the array.
On the 18 chips, the limit is the amount of RAM you have available.

On the original question, regarding the 'union', this is a way of making _two_ (or more) different 'types' of variable use the same memory area. So if (for instance), you create a union as: