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'[PIC] Voltage minimum for ICSP?'
2005\10\01@180933 by David de Regt

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I just did a bit more looking into this problem..  I'm wondering if the
voltages this programmer is putting out are a bit low.

The programmer is putting +10.3V to VPP/MCSP (pin 4), and only +3.2V to
VDD (measured against the ground pin.)  Looking up the specs in the
PIC16F88 datasheet, it doesn't actually say what VIHH is (though it
mentions it,) but all sites seem to use 13V for VPP and 5V for VDD.

Is it possible that these lower voltages are what's preventing this
other batch of PIC16F88s from being written, and that the other chip is
just barely tolerant enough to be written at the lower voltages?

-David

2005\10\01@190135 by Jan-Erik Soderholm

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David de Regt wrote :

> The programmer is putting +10.3V to VPP/MCSP (pin 4), and
> only +3.2V to VDD (measured against the ground pin.)  Looking
>  up the specs in the PIC16F88 datasheet,...

You should read the programming specification fir the chip, not the
regular data sheet. But then, any developer of a good PIC
programmer have already done that for you... :-)

> Is it possible that these lower voltages are what's preventing this
> other batch of PIC16F88s from being written, and that the
> other chip is just barely tolerant enough to be written
> at the lower voltages?

Vdd = 3.2V *could* be OK for *some* ICSP functions, but definitely
not for "Erase All" (which most programming operations
start with), that one needs at least 4.5V if I'm not wrong.

Jan-Erik.



2005\10\01@190329 by olin piclist

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David de Regt wrote:
> The programmer is putting +10.3V to VPP/MCSP (pin 4), and only +3.2V
> to VDD (measured against the ground pin.)  Looking up the specs in the
> PIC16F88 datasheet, it doesn't actually say what VIHH is (though it
> mentions it,) but all sites seem to use 13V for VPP and 5V for VDD.

Vihh (the programming voltage) is specified from Vdd+3.5 to 13.5V (DS39607B
page 18).  10.3V is actually within spec.  3.2V Vdd is definitely too low
for some operations.  It depends on what your programmer does, but this is
probably a problem.  It can't do a bulk erase, for example, which also means
it can't reset read protection bits.

You might want to consider a real programmer.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\10\01@190830 by olin piclist

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Jan-Erik Soderholm wrote:
> Vdd = 3.2V *could* be OK for *some* ICSP functions, but definitely
> not for "Erase All" (which most programming operations
> start with), that one needs at least 4.5V if I'm not wrong.

No, you're not.  According to the 16F87/88 programming spec, DS39607B, page
18, 4.5V to 5.5V is "Vdd level for Bulk Erase, Chip Erase, and Begin Program
operations of program and data memory".


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

2005\10\01@232943 by David de Regt

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So I figured out that if I hit "write" in ICProg, and then as soon as it
starts the process, plug in +5V to Vdd, I can get successful burns.

So, sounds like I need a new programmer, but this should tide me over
for a while anyway.  Thanks for the help, all. :)

-David

{Original Message removed}

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