Intro to microcontrollers (long)

[Bill Shaw]

Excellent dissertation, Steve.  Very clear and concise expalnation of the
inner workings of a HC11,  and it's application to the GM-ECM problem.  I'd
like to add,  for the programmatically challanged,  that this info (the
archetecture, perhiperals, instruction set, etc) is specific to this one
microprocessor,  but the general concepts described here apply to all
micros.

I'd also like to add that Terry's comment is correct.  *Most* of the people
using these GM-ECMs don't need to have this level of knowledge of assembly
language programming to use them,  modifying the tables will suffice.
However,  if you REALLY want to understand what's going on, or have some
major modifications to make (want to add nitrous to your quad-blown super 4
banger, but only use it when you have the bottle full?)  you *MAY* need to
do a little programming.

As far as disassembly is concerned,  this is a difficult task above and
beyond programming (I've done a lot of it).  You not only need to
understand the cpu archetecture and every nuance of each machine
instruction,  but you also have to decipher what the original author was
thinking when he programmed it.  There is an infinate variety of ways a
particular problem can be programmed,  as varied as all the individual
programmers. It also gets to be *much* more difficult to disassemble code
that was written using a compiler (C or Modula, for example)  as opposed to
assembly language. And I know for a fact there is no chance in hell of
getting the source code from GM.  Not even their 'blessed' subcontractors
can get it.  So,  reverse engineering is the only way to get insider
knowledge of these boxes.

Is GM really using Modula to program these boxes?

Bill