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

Tony Duell ard at p850ug1.demon.co.uk
Wed Feb 27 17:11:59 CST 2008


>    Well, Chuck said it best, but I'll add this: You get fewer  
> components, lower cost, easier maintainability and tweakability,  
> increased flexibility, the possibility for a reusable design...how is  
> this a bad thing?

OK, let's look at those advantages : 

'Fewer COmpoentns'. OK, I'll grant that there are probably few bits to 
pick up and solder to the PCB (although it's close -- as I mentioned last 
night, there's a CUTS decoder using a single 16 pin TTL chip). But there 
are certainly more 'devices' -- individual transistors, etc -- in the 
microcontrolelr solution. Now, my expoerience suggests that while a 
single chip is moree reliable than making the same circuit from many 
chips or discrete transistors, a complex chip _is_ less reliale than a 
simple one. So while trying to build the 'microcontroller' solution using 
TTL (full adders, lateches for the registers, etc) would be considerably 
less reliuable than the single chip microcontroller, I also suspect that 
a single TTL chip, or a few of them, would be more reliable than the 
microcontorller

'Lower cost'. I could make the flipant answer and say that my junk box 
contains plenty of TTL chips and no microocntrollers. But I'd rather 
point out that the cheapest solution is not necessarily the best, and 
that this idea of always cutting the cost to the minimum is one reason 
that I don't buy many new products. 

'Easier maintainabilty and tweakaility'. Surely you jest here! It is a 
lot easier to find a fault in a circuit when you can actually put the 
'scope probe on a particular signal. Darn it, with a single-chip 
microcontroller, you can't normally trace the firmware. Repairing it is a 
nightmare unless you have the firmware (prefereably as source code). I'd 
much rather change a 2-lead passive compoennt than reprogram a chip (and 
it'll be quicker...)

'Increased fleximbility'. The original discussion was to decode cassette 
tones. Why do I want to add any more features. I prefer a design that 
does one job, and does it well.

'Reuseable Design'. Again 'Why?'. I'd much rather come up with the 
_right_ design (IMHO) for each problem eather than try to kludge in a 
previous design just ecause I have it. This quickly leads to the idea of 
bodging together off-the-shelf units, which is another thing I dislike...

-tony



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