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Re: [avr-libc-dev] ATtiny 25/45/85 support

From: Joerg Wunsch
Subject: Re: [avr-libc-dev] ATtiny 25/45/85 support
Date: Tue, 31 May 2005 11:57:53 +0200
User-agent: Mutt/

As David Carr wrote:

> Is there a list of all SIG_* somewhere?

The avr-libc doc is supposed to have an exhaustive list of all names.

Alas, I recently noticed we are rather inconsistent in the naming.

> Also, where does
> the number in _VECTOR(#) come from?

It corresponds to the vector order in the datasheet, except the
datasheet starts numbering base 1 at the reset vector, while we start
base 0 at the reset vector (which is omitted), i.e. base 1 at the
first actual interrupt.

> Lastly, how is _VECTORS_SIZE calculated?

(last vector # + 1) * sizeof(vector slot)

Adding 1 takes care of the reset vector slot.  The slot size depends
on the device, it's 4 for the large devices, 2 for the small ones.
Remember the Atmel datasheet counts in 16-bit words, while we do count
everything in bytes.

> Also, when I looked at how the EEPROM SFRs are defined in io.h I
> noticed that there are few differences between the EECR bits of the
> tiny45 and the EECR bits in io.h.  Should I have an #ifdef block
> there to choose the correct set of EECR bit #defines or should we
> just move these defines into the device specific io headers?

See for example for the ATmega169 (which has been the first MCU with
the EEPROM devices in a different location): #undef the old values,
and define them to what is needed.

Sigh, we *really* need (partial) per-device libs.

> I noticed some errors (misnamed bits) in the register summary of the
> 25/45/85 datasheet, is this common?

Please report them to address@hidden  Yes, alas, it occasionally
happens there are some errors in these documents.  After all, we all
know how development works: marketing announces the availability of a
new device, and once it's eventually ready (a couple of months later
:), everything that's not considered to be crucial is rushed out of
the door...

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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