DPRG mailing list archives: [DPRG] Programming PICs at 3.3V through ICSP

Wed Apr 23 06:54:27 CDT 2008

The local Microchip FAE is Garry Champ champ at microchip.com
He is in Addison. I can help you with PIC24 but not PIC16F.

I also have a Needhams programmer that should be able to program it.
Needhams made good programmers but are now gone, which may be a surprise
to people, it was to me.

Kip

On Wed, 2008-04-23 at 00:14 -0500, Jeff Sampson wrote:
> Hi,
> 
> Is anybody using PIC processors? I have a need to program 2 types of 
> PICs with a VDD of 3.3V. I can't raise the VDD to 5V like Microchip 
> wants me to do.
> 
> This has to be done through the ICSP interface with our own custom 
> circuitry. I.e., I'm not looking to use an external programmer.
> 
> (Or at least about $50k worth of boards thing I should be able to pull 
> this off. ;-)
> 
> Their data sheets sort of hint that it can be done, but all of their 
> examples show using the 5V bulk erase.
> 
> The two parts in question are the 16F917 and the 16F886. They are both 
> new enough to have row erase commands and I am able to erase program 
> space at 3.3V. I can't seem to erase config space at 3.3V, mainly 
> because I can't figure out from their data sheet how to do it. Or is 
> config space really considered program space? Again I can't determine 
> that from their data sheet.
> 
> (Another confusing factor is that bulk erase appears to work on program, 
> config and EEPROM at 3.3V, even though they say it will not work at 
> lower than 4.5V.)
> 
> I did have an inspiration while I was doing another futile Google search 
> tonight. The ICD-2 programmer does apparently program the chips. And the 
> VDD on the board is at 3.3V. I checked with a scope and it is not 
> raising VDD to 5V. So they may be using the elusive command sequence 
> that I am looking for, or they are using bulk erase and it just happens 
> to work.
> 
> So... I am going to connect my scope tomorrow and count bits to see what 
> commands they are sending. But if someone happens to know the trick, it 
> will save me a lot of bit counting. :-)
> 
-- 
Kipton Moravec KE5NGX
"Always do right; this will gratify some people and astonish the rest."
--Mark Twain