WebSales wrote:
> Can the code be changed so bulk erase is not necessary ?

Most PICs have different erase and write algorithms available that work at
lower voltages.  These can not perform all operations and can not recover
from a PIC in an arbitrary state.  They could be used in theory if you are
careful never to set code protection, and perhaps some other settings.

The code *could* be changed for this special case.  However that would
require significant work and testing, and is something I would not do unless
there was serious $$ attached to it.  For example, if someone offered NRE or
ordered 50 ProProgs with the stipulation they can work at low Vdd only I
would probably agree to do it.

In the mean time, all I can say is that the host source and EasyProg
firmware are open and available at http://www.embedinc.com/picprg/sw.htm for
anyone that wants to attempt this themselves.

> I do not want to change the hardware.

ICSP is not hard to accomodate if considered during the design, but if not
it can lead to situations exactly like this.  Unfortunately Microchip
doesn't point this out up front.  On the other hand, most people don't look
until they're ready to go to production.  Once it's too late, there is no
good answer.

> If the supply is not on board then there has to be provision to isolate
> all the 3V circuitry during programming (for applications with size
> constraints it is a pain top find room for additional headers or jumpers
> that are simple enough and safe enough for end users to access.

Usually an extra schottky diode or two is all that's required.  Sometimes
less depending on how the power supply works.


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