[TimCraig]

If you have specific questions, feel free to contact me directly. I haven't worked with AVRs but I've poked around at the processor level on PCs of all ages and, of course, the PIC robot controllers. It can't be that obtuse.

If you're looking at C/C++, pay particular attention to the difference between the logical operators, &&, ||, and !; and the bitwise operators ~, &, |, and ^. Look up the descriptions of "masking" for isolating and manupulating individual bits.

In a somewhat related vein, it's helpful to know if your system represents multibyte variables in little endian or big endian form. (The origin of those terms is kind of interesting)

Another architectural detail is how I/O is addressed by the CPU. Is there a separate I/O address space or is it mapped to the memory space of the processor. Desktop applications generally don't care about this but with a lot of smaller embedded systems, you're on your own.