Re: [avr-gcc-list] AT90CAN128 support

[Henrik Maier]

Ned Konz wrote:
> What is needed for AVR-GCC to support the AT90CAN128 () that isn't 
> already provided by the Atmega128 support?

The AT90CAN128 has a completely different register structure and 
location and for that reason is not binary compatible with the 
ATmega128. This affects mainly the avr-libc library and your application 
code rather than the compiler, as the instruction set is identical.

Refer to Atmel's APP note AVR096 which explains the differences:
http://www.atmel.com/dyn/resources/prod_documents/doc4313.pdf

> That is, why not just use
>
> -mmcu=atmega128
>
> for the AT90CAN128?

Won't work and you can even kill your MCU by doing this. You are very 
likely to initialise the peripherals wrong.

> That's what I was planning on doing; is there some reason why that 
> wouldn't work?
> Did I miss an important detail somewhere (uh oh... gotta read the 
> datasheet)?

Always a good idea to study the reference material first.

> You might need to supplement avr-libc by adding some register/bit 
> definitions for added CAN hardware or maybe slightly different linker 
> scripts, but this can be done by the user and has no impact on AVR-GCC.

This already has been done a fair while ago and since avr-libc 1.2.5 the 
AT90CAN128 is properly supported including EEPROM.

Henrik
http://www.proconx.com