Linux programmer for the Atmel ATmega8

For various projects, I have used the Atmel AT90S1200 and AT90S4433 microcontrollers. Recently, the ATmega8 has been introduced as an enhanced version of the 4433, so I am using the ATmega8 for some robot experiments.

I use Linux for my normal working environment. Hardware is developed using the Eagle PCB layout package. For software development I use the Tavrasm assembler, available from www.tavrasm.org. To download programs to the target processor, I use a homebuilt board connected to the PC printer port, with the SP12 programming software. SP12 is available from Steven Bolt at www.xs4all.nl/~sbolt/e-spider_prog.html

Now for the fun. None of these tools support the ATmega8. For Eagle, I built my own device libarary by modifying the existing 4433 model. For tavrasm, it's a couple of lines changed to support a new .device instruction.

SP12 supports some mega chips, but not the ATmega8. After a day of hacking, I was able to download a program to it, and reprogram the flags.

For burning, there are two main differences between the ATmega8 and other Atmel chips:

There are a lot of extra flags. In particular, there are flags to switch between an internal RC oscillator, external crystal, or an external resonator as the clock source. The chip comes from the factory programmed to use the internal RC oscillator, so I definitely needed to reprogram those flags.
The program memory is written in pages of 32 instructions; other mega devices appear to use a page of 128 instructions.

Source code for my modified version is posted as sp12mega8.tgz (depending on your browser, you may have to right-click or shift-click this link to download the file). NOTE: this is a quickly hacked version, with several restrictions, including

It has been tested on linux only.
It has been tested with the ATmega8 only. The hacks may have broken it for other chips.
The new -X option sets flags in the low flag byte only.
The SP12 flag options (-V0, etc) probably don't work.
Options to set the memory protection fuse bits or the upper byte of flag bits have not been fully implemented.