> In the meantime, I've been researching other microcontrollers, mostly
> the Microchip PIC.  I must say it has been quite an effort trying to
> figure out the product line, which chips are history, what to use
> where and so forth, but I'm beginning to see the method to the
> madness.

did you read http://www.voti.nl/swp? You did find the Wisp628, so you
probably have.

> It seems as if the only features the fancy (i.e. expensive)
> (snip)  
> Is there more that I'm missing here?

Good summary.

> It doesn't really seem as if the very simple programmers based on
> AN589 or COM84 really do anything different that the fancy-pants
> programmers, so long as you get the programming signals on the proper
> pins.

If you can get it to work the simple proggers are OK, but when you have
spend a few weekends without success that's a very big 'if'. OTOH it can
save you some money. And serial/parallel port bit-fiddeling progger
software can be a PITA on NT/XP type systems.

> It seems as if the electrical characteristics of the AN589 circuit are
> standard for all recent PICs, and it is the software dataflow that
> really determines what chips can be programmed.

correct

> Then there is the issue of in-circuit programming.  It seems as if
> in-circuit programming uses the same programming functions and signals
> as the "standard" programming, and doing in-circuit programming is
> more a matter of designing the embedded circuit with proper isolation
> to accept in-circuit programming.

It is also a matter of having a progger that can handle the higher load
likely to be present when a target chip is programmed in-circuit. 

> This *seems* as if it would be a very simple and elegant solution to
> development and prototyping, yet I have found only a few references to
> this method. (Wisp and TLVP) Furthermore, it seems as if this method
> will easily allow the use of the LVP, eliminating the need for the 13v
> supply & associated circuitry.  Are there issues involved that I am
> missing?  Are there cases where this doesn't work?

when it does not work this is mostly due to a too feeble drive of the
programming pins.

> Right now, I'm leaning towards using Byron Jeff's design for the

fine, as long as
- you use part that are LVP (12F629 etc are not!)
- you don't need the LVP pin (it is claimed by the LVP feature)

> number of simple PICs, and it looks like the 12F629/16F630 will fit

Note that to (re)program this part with /MCLR configured as Input pin
you will need to power cycle the chip as part of the programming
process, this is an extra design thing for ICSP.

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: www.voti.nl/hvu
 

_______________________________________________
http://www.piclist.com
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist