1st stage loader for IMSAI - need ascii to binary conversion

[Dave McGuire]

On Feb 28, 2008, at 2:12 PM, Tony Duell wrote:
>>    In the context of a small microcontroller like the ones we're
>> talking about, these things just don't have that much code space.
>> Almost none of them allow self-modifying code.  Nearly all of them
>> have small, simple instruction sets.  If the programmer NEEDS to
>> actually trace the firmware to find a bug, I'd question that
>> programmer's competency.  Seriously.
>
> OK, so I;m an incompetent programmer. I'm happy to agree to that.  
> Because
> I certainly deug firmware (where possible) by hanging a logic analyser
> off the address lines and seeing where the code is going. If you  
> can do it without, great!.

   So do I, when I can't find a bug by reading the source code.  My  
point is that these smaller processors are so simple that it's damn  
difficult to write a bug that's impossible to find without wanting to  
probe the internal circuitry of the chip.

> Let me give you an alaogy. _I_ once tracked down a logic fault in a  
> P850
> by noticing some odd behviour of the front panel bulbs, in particular
> that half were brighter than the other half. Knowing that it's  
> really an
> 8 bit machine interlally made me suspect that one half of the data  
> wasn't
> being latched properly. That lead me to a missing latch strobe signal,
> and so on.
>
> On the other hand, most of the time I use a 'socpe and/or logic  
> analyser.
> I like to debug by figuring out what the unit is doing and  
> comparing it
> with what it should be doing. And I like to debug firmware the same  
> way.

   Sure, that makes sense.  But for what we're talking about, you  
honestly don't think that's overkill?  I too have a logic analyzer; I  
use it with some regularity and I'm comfortable with it...but in such  
a simple application, it'd likely take longer to hook up all the  
logic analyzer pin grabbers to the circuit than it would to find a  
bug in my own code running on a tiny processor with 1KB of program  
memory.

   Goal-oriented methodology isn't always a sellout.

          -Dave

-- 
Dave McGuire
Port Charlotte, FL