On Saturday, Dec 6, 2003, at 09:15 US/Pacific, James Sears wrote:

> What are the advantages of using a bootloader vs. In-Circuit Serial
> Programming?
>
On advantage is that at least theoretically, you move the details of
the programming algorithm from the pc-side software to the bootloader
firmware in the chip itself, and don't have to worry as much about
the differences between a 16f818 and 16f818a.  On the other hand,
it does end up looking an awful lot like just another type of
serial programmer.  Most of motorolas microcontrollers, an some of
the TI parts have used bootstrap loaders (hidden in rom, so when you
set some external pin, the boot rom executes instead of the user
programmed eprom) for a long time, but they still call their low
cost development systems that they call "programmers" - by the time
you say "you need these pins, and your need the crystal freq to be
xy.z MHz, and you need a 12V supply for VPP", I'm not sure that it
makes that much difference.

I suppose that technically, the difference between a boot loader
and ICSP is that the bootloader has fewer timing dependencies.
You need to get a serial bitrate right, but there's less of
the "assert x and strobe y for 5ms."  This puts a lot less pressure
on PC software that is increasingly unable to produce tightly timed
external signal changes.

I fair number of the bootloaders available provide some sort of
debugging environment as well (in fact, i think the bootloader
capable PICs are tagged as "supports ICD" in the microchip
parametric tables...

BillW

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