[avr-libc-dev] Re: Iotn13.h

[Theodore A. Roth]

On Thu, 20 May 2004, Bruce Graham wrote:

> Ted,
>
> Here is my suggested patch for the header iotn13.h  I did not test it
> very well since I have been unable to run "avr-as" by itself
> successfully.  I seem to be short the right document, which I probably
> have but can't find, or less likely don't have and can't find.
>
> Some things may be controversial:
> (1) When there is no External Memory -- should XRAMEND be 0? or should
> it be equal to RAMEND.  Actually I could go either way and I can't see
> where the symbol is used -- probably in malloc.

If the device has sram, XRAMEND must be >= RAMEND. The only devices that
have set XRAMEND = 0 don't have any sram and RAMEND is set to 0x1f
(r31).

> (2) Although PB5 is a handy shorthand, the tradition for bit names seems
> to be:
>     (a) use the data sheet name if a name is given
>     (b) concatenate numbers to the register name if a name is not given

See include/avr/portpins.h. We map PORTxn to Pxn there.

Refs:
  http://mail.gnu.org/archive/html/avr-libc-dev/2003-10/msg00026.html
  http://mail.gnu.org/archive/html/avr-libc-dev/2003-10/msg00045.html

> (3) I was not sure what SPEN referred to in register SPMCSR.  I could
> not find it in the data sheet, nor could I find it in one or two other
> data sheets I checked.  I hope it was just a mistake, but I could
> believe it came form an earlier version of the family.

That's a bug. It should be SPMEN to allow the include/avrboot.h header
file to work.

All the comments look fine. I'll commit this (minus the XRAMEND change
in the morning sometime.

Thanks.

---
Ted Roth
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