Programming PIC without erasing EEPROM

MarcosAmbrose · Joined: 25 Sep 2006 Posts: 38 Location: Adelaide, Australia

Everytime re-compile and upload new code to my target board, the ICD-U40 erases the EEPROM.

"PCM programmer" posted a link in previous post which had the same problem, but the link doesn't work anymore. "PCM programmer", can you or anyone else recall what the solution was? -Cheers

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Here is the information from that link:

Dimmu · Joined: 01 Jul 2007 Posts: 37

Is it normal that I do not see the "Erase when needed" option but only the "bulk erase" and the "no erase" options in the Erase modes section ?

I found that the Erase and Burn section allows to prevent the EEPROM from being programmed, but the tools often resets my settings. Is it a special way to force this setting -but still the best option would be to used the famous erase when needed...- ?

Dimmu

nilsener · Joined: 06 Dec 2005 Posts: 59

Hello Dimmu,

Sorry for reactivating this old thread. I have the same problem but with Microchips MPLAB ICD2. It seems to be impossible to reprogram the PIC with new software without erasing the EEPROM that is Code Protected in this case. My data in EEPROM must not be erased as it contains calibration data.

Have you solved your problem with the ICD-U40 to program (not to debug) the PIC while don't erasing the EEPROM? Then I will buy an ICD-U40.

Best Regards
nilsener

Dimmu___ · Guest

Nope,

Never found a good way to do this.

On the other hand, I didn't touch a PIC for about 1 year now, so maybe the softwares have been updated since.

Best regards
Dimmu

collink · Joined: 08 Jan 2010 Posts: 137 Location: Michigan

It's very easy to program a PIC chip without touching the EEPROM if you use a pickit 2 or 3 with their software. So that's a possibility if you have no other way to do it. Pickit2 is pretty cheap.

JH1987 · Joined: 22 Jan 2011 Posts: 11

JH1987 · Joined: 22 Jan 2011 Posts: 11

andrewg · Posted: Sat Jan 22, 2011 9:35 pm

What you want to do is theoretically possible, but not with your current hardware (programmer) and software.

Microchip have a relevant programming specification document:

http://ww1.microchip.com/downloads/en/DeviceDoc/39622L.pdf

See section 3 on page 14. There are specific commands to selectively erase portions of code memory, allowing it to be reprogrammed. However, I don't know of any package to let you do this, so you'll either have to develop one yourself (and corresponding hardware), or find some open source PIC programmer software that you could modify.
_________________
Andrew

JH1987 · Joined: 22 Jan 2011 Posts: 11

andrewg · Posted: Sun Jan 23, 2011 10:01 pm

JH1987 · Joined: 22 Jan 2011 Posts: 11

Hey Andrew,

I actually did see the sentence "A Bulk Erase is the only way to reprogram
code-protect bits from an ON state to an
OFF state."

But since the bulk erase operation is configurable, I thought you could set the Bulk Erase Control registers to something like Erase Configuration Bits (0082h) and then execute the bulk erase. I wonder if that would turn off code protection. Like you say, Microchip takes code protect seriously, so maybe the IC has another safeguard. And you're right, they do say you have to erase data EEPROM when protected. But you'd think if you could do that bulk erase and clear the config bit, then you could get to the EEPROM. It might make an interesting experiment...

As for the factory debug feature, I could definitely do that. I was trying to replace the code in the PIC with code that did almost exactly that. For me its easier just to turn of CPD, since that EEPROM data really doesn't need to be protected. For somebody that needs protection, your option is better.

Thanks for your reply.