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PICList Thread
'[PIC]: Oscillator Speed & Code Protect Lock'
2002\04\14@024124 by Rajiv Thakur

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Hi all,

I am relatively new to PIC. I need feedback on the following:

1. Can a 16F84-20/P be run on lower spped of  4 Mz or 1 Mz. What will be the
oscillator setting for 4 Mz (XT or HS)

2. The PIC start Programmer/Warp13A programmer does not erase the locked
code on my 16F84-20/P when I press Program Erase or Bulk Erase. The chip
does not accept programming again.Any feedback as to what should be done to
make the chip programmable again.

Thanks

Rajiv Thakur

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2002\04\14@030926 by Kevin Howell

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Yes you can use a lower speed crystal. You can specify either XT or HS in my
experience...

As far as I know, once you've enabled code protection you can't reverse it.

Regards
Kevin Howell


{Original Message removed}

2002\04\14@082510 by Byron A Jeff

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On Sun, Apr 14, 2002 at 11:56:59AM -0700, Rajiv Thakur wrote:
> Hi all,
>
> I am relatively new to PIC. I need feedback on the following:

Since you are new let me give you some helpful advice: drop the 16F84 and
move up to the updated 16F628. It's a better part all the way around and
is generally cheaper than 16F84 parts.

>
> 1. Can a 16F84-20/P be run on lower spped of  4 Mz or 1 Mz. What will be the
> oscillator setting for 4 Mz (XT or HS)

Yes. And that had better be a 16F84A, which is the only 16F84 type part that
runs at 20 Mhz. Choose XT in the 1-4 Mhz range.

>
> 2. The PIC start Programmer/Warp13A programmer does not erase the locked
> code on my 16F84-20/P when I press Program Erase or Bulk Erase. The chip
> does not accept programming again.Any feedback as to what should be done to
> make the chip programmable again.

It has to be a programmer software issue. A Bulk Erase will erase the code
protect bits thus unlocking the chip again. There is no way to permanantly
code protect any PIC flash based chip.

And on a slightly humorous note, since that 16F84 is completely locked up,
this is a great time for you to upgrade to the 16F628!

Good luck on getting your part working again.

BAJ

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2002\04\14@100716 by Olin Lathrop

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> 1. Can a 16F84-20/P be run on lower spped of  4 Mz or 1 Mz. What will be
the
> oscillator setting for 4 Mz (XT or HS)

All PICs are fully static, and therefore work with any clock from DC to the
specified maximum.  Of course this isn't true of the crystal driver.  XT
should work at 4MHz, see manual.


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2002\04\14@113553 by Glen Wiley

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On Sun, Apr 14, 2002 at 11:56:59AM -0700, Rajiv Thakur wrote:
> Hi all,
>
> I am relatively new to PIC. I need feedback on the following:
>
> 1. Can a 16F84-20/P be run on lower spped of  4 Mz or 1 Mz. What will be the
> oscillator setting for 4 Mz (XT or HS)

Specifying XT rather than HS for 4 MHz can save considerable power
(important if your design is supplied via battery for example).
According to the datasheet, at 4Mhz, 5V using HS will draw a
typical IDD of 2.1mA, using XT will only draw 0.22mA

<snip>

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Glen Wiley

Those who can - code.

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