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'[PIC]: Bulk erasing code protected 16F87x devices'
2002\09\06@081714 by Alan Gorham

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Hello

I'm doing ICSP on 16F874's using a PICSTART+
If I program the devices with code protect on and then try to reprogram them
I get the "configuration bits not set"
error message from MPLAB.

I asked the local Microchip Tech Support about this and he said that I
should be able to perform a bulk erase by
just clicking the "Erase Flash Device" button on the PICSTART window.

If I do this, then the "active" LED on the PICSTART flashes for a fraction
of a second, but nothing else seems to happen.

I'm using v5.70 of MPLAB and v3.00 of PICSTART firmware.

Do I need a production type programmer to do a bulk erase, or is the problem
down to the in-circuit nature of the programming?


Thanks


Alan

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2002\09\06@093502 by John Walshe

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Hi Alan,
   As you know the Picstart is "not supposed to be used for ICSP" - however
I also use it all the time for ICSP. But however, you do have to watch the
wire lengths(a few cm at max) and the load that the "other circuitry is
presenting to the PS+ (it has zip of a drive capability). Make sure nothing
else is connected to the VDD line and try it again(I assume RB6&7 are
buffered adequately from the circuit). I've recently had a problem
programming a 628 where the code was getting in the first time but second
time it was screwed up and config bits were not being set etc (similar to
your case) - the offending item was a 100nF cap across the VDD/VSS near the
pic. Removed that, and everything worked perfectly.
You could also check that the clock hasn't started to oscillate - it
shouldn't when programming.

John
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2002\09\06@102912 by Roman Black

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Hi John, I use the PSP for ICSP on many projects,
and have never had a problem with it. I typically
have the wires from 30 to 60 cm length, with never
a bad program or verify. Are you using ribbon cable?
That will have much higher capacitance than just
running 3 wires between the sockets. The reason I
say 3 wires is that I run the ground wire from
the PSP socket to the board ground of the target
board totally separate from the 3 other wires.

The 3 wires are cabled tied loosely together and
run maybe 15cm away from the ground wire. I have
good cap meters here and can measure the
capacitances if you like. :o)
-Roman


John Walshe wrote:
{Quote hidden}

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2002\09\06@105547 by Alan Gorham

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Hi John

I should point out that I have *NO* problems programming/reprogramming the
device *without* setting the code protect bit.
I must have reprgrammed my development PCB 10,000's times without problems!

The problem is only when I set the code protect bit, program and then try to
reprogram.

Alan

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2002\09\06@112222 by Jennifer L. Gatza

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> If I do this, then the "active" LED on the PICSTART flashes
> for a fraction
> of a second, but nothing else seems to happen.

The bulk erase occurs very quickly, so the LED flashes so quickly I often
don't even notice it.  After you erase the chip, click the "Blank" button to
verify that the chip was erased successfully.  If it does not report "Device
is blank," try another chip.  If it still doesn't erase, start checking
errata sheets.

Jen

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2002\09\06@115056 by Alan Gorham

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Hi Jen

>The bulk erase occurs very quickly, so the LED flashes so quickly I often
>don't even notice it.

That sounds familiar...


>After you erase the chip, click the "Blank" button to
>verify that the chip was erased successfully.  If it does not report
"Device
>is blank," try another chip.

Tried it with 400 :-)

> If it still doesn't erase, start checking errata sheets.

I'd better!

Thanks

Alan

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2002\09\07@072326 by Alan Gorham

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An update:

I can bulk erase code protected chips if I insert them into the ZIF socket
on the PICSTART.
So now my problem is still with doing a bulk erase via ICSP.
My question is now:
Why do I have problems doing a bulk erase via ICSP, when I have no problem
programming
via ICSP?


Alan

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2002\09\07@093247 by Jason Harper

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Alan wrote:
> Why do I have problems doing a bulk erase via ICSP, when I have no
problem
> programming via ICSP?

Generally, bulk erase requires 5V, but all other programming functions work
over the full rated supply voltage range of the PIC.  Is power to the chip
coming from the circuit or the programmer when you're doing ICSP?
       Jason Harper

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2002\09\09@045348 by Alan Gorham

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Generally, bulk erase requires 5V, but all other programming functions work
over the full rated supply voltage range of the PIC.  Is power to the chip
coming from the circuit or the programmer when you're doing ICSP?
       Jason Harper



The PICSTART supplies the power during programming, but I normally have LVP
turned off.
Is this my downfall?
I'll test this and see....

Thanks

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