Olin Lathrop wrote:

>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.
>
>  
>
This is the reason that companies get into trouble when they seperate 
firmware development
from hardware development. Before you design something, you need to hire 
Olin or somebody
else who can study your design and make sure you can accomplish your 
goals. This is not a criticism
of YOUR company, I've seen this repeatedly all over. Its a kind of 
mismanagement, and MicroChip
isn't very helpful, either.
 
Except for simple projects, all future embedded designs will including 
at least minimal HV ICSP
programming, with most updates being done by "bootloading" part of the 
firmware. Frankly, I
have NEVER understood the need for  LVP, but I thought maybe I'd 
overlooked something.

>>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.
>>    
>>
>
>  
>
sometimes it is a matter of re-specifying the components so that they 
can tolerate 5V
during HV programming.

--Bob

>Usually an extra schottky diode or two is all that's required.  Sometimes
>less depending on how the power supply works.
>
>
>******************************************************************
>Embed Inc, Littleton Massachusetts, (978) 742-9014.  #1 PIC
>consultant in 2004 program year.  http://www.embedinc.com/products
>  
>


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