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Beware ICD-U40 will destroy chips.
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bdavis



Joined: 31 May 2004
Posts: 86
Location: Colorado Springs, CO

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PostPosted: Wed Aug 04, 2004 9:57 am     Reply with quote
Sorry for the confusion of frying the chips.

I saw a post on the microchip forum asking if there are any issues using the ICD2 with the target chip Vdd at 3V, and the moderator said no issues at all, just follow the programming/running operation of the chip.

I also sent the below questions to CCS support concerning 3.3V operation:

[email sent]
Quote:

Questions concerning PIC 3.3V operation:
1.) Your supported ICD listing of chips do not list the PIC18LF452 (or many LF chips). Is the PIC18LF452 running at 3.3V supported by the USB ICD-U40?

2.) Does the ICD-U40 support ICD with the target at 3.3V? What about ICSP with the target at 3.3V?

3.) Can I use the bootloader and download new firmware with the target
running at 3.3V?

4.) If I need to clear/change the configuration fuses, can the ICD-U40 do
this on a target running at 3.3V?


[email received]
Quote:

1. The LF chips are the same from a software point of view as F chips.
The config bits are the same as well as everything else. Because of this we did not enter these chips separatly in our database.
2. Yes to both. You do need to connect your target Vdd to the ICD-U40.
3. Yes.
4. Yes in most cases. If the chip is code protected then this can only be
cleared at 5V.

Based on this, and reading the programming specification, I had thought the only bits that require Vdd of 5V are the code protection bits, and all other fuses/configuration bits may be set and cleared while the Vdd=3.3V.

Is this true? If the DEBUG configuration can't be set and cleared at Vdd=3.3V, I don't see how they can claim 3.3V operation. I had thought that all fuses could be set/cleard at Vdd of 3.3V if Vpp was set to 13V, but I no longer think this is the case.

Can you set and clear any of the configuration bits/fuses other than the code protection bits?
Guest
Guest
Duh
PostPosted: Thu Aug 05, 2004 8:08 pm     Reply with quote
Lets blam CCS for not understanding your target chip and not taking time to understand how your target it programed and erased.

Sure it would be nice for them to warn poeple should they have to?
I dont think they have to no.

Lets see. Instructions on a Gun should read

Dont aim gun at head and pull trigger.
bdavis



Joined: 31 May 2004
Posts: 86
Location: Colorado Springs, CO

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PostPosted: Sat Aug 07, 2004 10:28 pm     Reply with quote
I don't think it's a Duh! - ie: common sense. Many people have run into the problem, and it is not CCS's fault, but they COULD help! A simple statement of low voltage vs high voltage programming, and that it has nothing to do with the Vdd voltage required to do a bulk erase. I only saw it on the data sheet, and there was no clarification on it - yes - Microchip COULD help to by writing just as few lines stating that at Vpp of 12V (or lower), that you can perform a bulk erase at 4.5-5V Vdd, but NOT at 3.3V, AND specify what configuration bits can be set and cleared without a bulk erase. Why do you think they have had questions on this for so long, and there are no replies with specific 3.3V usage? ( 99%, as a guess, seem to be using 5V and never see the issue.)

It's not anyone's fault, but is frustrating finding specific information on it, and the High vs Low voltage programming confuses the issue. (ie: even with High Voltage programming, you can't do a bulk erase to clear code protection configuration bits, but you can do a bulk erase with Low voltage programming with Vdd=5V).

To summarize using 3.3V Vdd using the ICD-U40 with ICSP - Never enable code protection, and you should be fine. If you enable any code protection, you can't remove it without removing the PIC or putting 4.5 to 5 volts on Vdd. Hope this is useful to others in the future.
Guest
OK the system is now running at 5 Volts
PostPosted: Tue Sep 28, 2004 11:10 am     Reply with quote
Darren Rook wrote:
Doesn't ICD-2 have the same problem?


Darren.
Back to this old issue. I just got time to mount that PIC18F6720 and a blank board and, provided crystal and power at 5 Volts.

The part will not erase fuses.

Hans Wedemeyer
Darren Rook



Joined: 06 Sep 2003
Posts: 287
Location: Milwaukee, WI

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Re: OK the system is now running at 5 Volts
PostPosted: Tue Sep 28, 2004 3:56 pm     Reply with quote
Anonymous wrote:
Darren Rook wrote:
Doesn't ICD-2 have the same problem?


Darren.
Back to this old issue. I just got time to mount that PIC18F6720 and a blank board and, provided crystal and power at 5 Volts.

The part will not erase fuses.

Hans Wedemeyer


I am confused with what you are saying...

Are you saying that MPLAB ICD-2 will not erase fuses at 5V after it was programmed at 3.3V? Or the ICD-U40?
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Tue Sep 28, 2004 5:47 pm     Reply with quote
The ICD2 will definately do it or my name is not Mark Wink
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