Re: [avr-libc-dev] Question on IO header policy

[David Brown]

Weddington, Eric wrote:
> Hi All,
>
> The avr-libc project has had a policy where all register names and bit
> names in a device IO header file are derived directly from the Atmel
> device datasheet. We then updated that policy to state that those names
> are derived directly from the Atmel device XML files that are shipped
> with AVR Studio.
>
> There is a WinAVR bug, #1883630, where a user is requesting the addition
> of some *alias* bit names to the IO header file(s) for the
> ATmega164P-324P-644P devices.
> <http://sourceforge.net/tracker/?func=detail&atid=520074&aid=1883630&gro
> up_id=68108>
>
> In doing a search of the latest datasheet for those devices, the
> requested names (UCPHA0 and UCPHA1) are *not* found on the datasheet. In
> doing a search of the relevant XML files for those devices I find that
> those names exist, but with an ALIAS tag, for example:
> <ALIAS>UCPHA0</ALIAS>
> Where this alias is after the true listed bit name.
>
> This is the first time that I have run across this ALIAS tag in the XML
> devices files.
>
> The question is, should avr-libc provide these alias names? Or should
> avr-libc only strictly provide the real bit names, that are also found
> in the datasheets?
>
> Thanks,
> Eric Weddington

I haven't looked at the xml files to see these aliases, but one use I 
can think of for aliases is compatibility between AVRs.  For example, an 
AVR with one uart would have a status register called UCSRA, while its 
big brother with two uarts would call the same register UCSR0A.  This 
sort of thing can be an unnecessary pain when converting code from one 
AVR to another.

Other than that, I think most people only ever read the datasheets, not 
the xml files - names that only appear in the xml files are therefore 
probably of little use.

mvh.,

David