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'[PIC]: Any programmer good for ICSP'
2002\05\17@105224 by Tal Dayan

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Can any programmer that can program 16f84 be used also to program 16f84
in circuit ?

In my specific case, this is the El Cheapo Programmer.

Thanks,

Tal

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2002\05\17@110506 by uter van ooijen & floortje hanneman

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> Can any programmer that can program 16f84 be used also to program 16f84
> in circuit ?

Definetely no (although some cn). What can somethimes help is to remove the
crystal while programming.

Wouter van Ooijen
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2002\05\17@145115 by Byron A Jeff

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On Fri, May 17, 2002 at 07:50:07AM -0700, Tal Dayan wrote:
> Can any programmer that can program 16f84 be used also to program 16f84
> in circuit ?

Doubtful. The clock causes some real issues. I'm experiencing this myself
with my Trivial LVP programmer:

http://www.finitesite.com/d3jsys

in its current state it has issues with the internal clock oscillator.

>
> In my specific case, this is the El Cheapo Programmer.

The programmer isn't really the issue, the target is. Some tips:

1) Be sure that there are resistors between the programmer's CLK/DATA pins and
the target. This ensures that if the target sets those pins to outputs that
buffers don't get blown.

2) Be careful with MCLR. Be doubly careful because often MCLR is either tied
directly to Vdd or pulled up through a resistor. If the pullup resistor is
already in place then you are probably OK. However you'll have a problem if
it's tied directly to the power supply. Be sure that the programmer has enough
juice to pull the pullup resistor to low.

3) The clock is a major issue. If it's running when you try to program it'll
often screw your programming process up. I've found that an external oscillator
through a resistor is ideal because you can then add a transistor to pull the
clock line low when programming. Does anyone know of the effect of an inline
resistor between a crystal and OSC1?

4) Lastly the programmer needs to be able to control Vdd. So the programmer
needs to be able to power the target.

Just a couple of final notes. First is that I use 16F877 parts precisely
because they are self programmable and so all of the issues go POOF! like
magic because the part is running normally. Second is the standing info
about 16F84s. They are obsolete. Check out the reasons:

http://www.finitesite.com/d3jsys/16F628.html

Hope this helps,

BAJ

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2002\05\17@155627 by uter van ooijen & floortje hanneman

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> Be sure that the programmer has enough
> juice to pull the pullup resistor to low.

And more important, to pull it high to 13 Volt!

> 3) The clock is a major issue. If it's running when you try to program
it'll
> often screw your programming process up.

That is essentially the same problem: /MCLR must be pulled up to 13 Volt
*quickly* (expressed in the number of clock cycles, hence removing the
crystal or having a low frequency will help somewhat).

> 4) Lastly the programmer needs to be able to control Vdd. So the
programmer
> needs to be able to power the target.

Why?

Wouter van Ooijen
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Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen

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2002\05\17@185511 by Mark J. Dulcey

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Byron A Jeff wrote:
> On Fri, May 17, 2002 at 07:50:07AM -0700, Tal Dayan wrote:
>
>>Can any programmer that can program 16f84 be used also to program 16f84
>>in circuit ?
>
>
> Doubtful. The clock causes some real issues. I'm experiencing this myself
> with my Trivial LVP programmer:
>
> http://www.finitesite.com/d3jsys
>
> in its current state it has issues with the internal clock oscillator.

> 3) The clock is a major issue. If it's running when you try to program it'll
> often screw your programming process up. I've found that an external oscillator
> through a resistor is ideal because you can then add a transistor to pull the
> clock line low when programming. Does anyone know of the effect of an inline
> resistor between a crystal and OSC1?

I believe that to reliably program parts with internal oscillators, your
programmer design has to be able to control Vcc as well as Vpp (for high
voltage programming) or RBn/PGM (for low voltage programming, where n=3
for the 16F87x, 4 for the 16F62x, or 5 for the 18Fxxx). The idea is that
you avoid powering up the part until you're ready to program it; you
have to raise both simultaneously or nearly so, so that the program on
the chip doesn't start running before you get it into programming mode.
(Unless you have disabled the power-on reset timer, you have 72
milliseconds before the code starts to run.)

This clearly presents real problems for an ICSP design, since you
generally won't have such control over the main power supply lines. I'm
not sure what the answer is then.

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2002\05\17@221053 by Tal (Zapta)

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We are using an external RC oscilator. Does this means that once we program
the
'blank' chip to use external oscilator, we can then program it in circuit
while
disabling the external oscilator (e.g. by short circuiting the RC capacitor)
?

(I would like to use the El Cheapo http://www.myke.com/elcheapo.htm with
16LF84)

Thanks,

Tal


> {Original Message removed}

2002\05\18@121421 by Arkady Skorokhod

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Hello,

May I add some questions here?

>The idea is that
> you avoid powering up the part until you're ready to program it; you
> have to raise both simultaneously or nearly so, so that the program on
> the chip doesn't start running before you get it into programming mode.

From Microchip's PIC12C5XX Eprom Memory Programming Specification
(DS30557D p.5):
"The MCLR pin should be raised from Vil to Vih within 9 ms of Vdd rise".

From Microchip's PIC12C67X ICSP Programming Specification
(DS40175C p.4):
"The MCLR pin must be raised from Vil to Vih before Vdd is applied".

1. Is it really important to use these different strategies for different
parts?
Isn't it always possible to apply the Vpp first and then apply the Vdd?
Say, in case of an in-circuit programming, apply the Vpp and then
switch on the target device. Is it safe to have Vpp ON and Vdd OFF for a
"long" time?

> (Unless you have disabled the power-on reset timer, you have 72
> milliseconds before the code starts to run.)

2. On the other hand, isn't 72ms quite a long time to not bother about these
Vpp BEFORE Vdd or AFTER?

Thanks,

Arkady

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2002\05\18@132219 by Mark J. Dulcey

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Arkady Skorokhod wrote:
{Quote hidden}

My point was that most of the simple programmers don't control Vdd at
all; they apply power to the chip as soon as you insert it or power up
the programmer. This may not be within the Microchip specs, but it works
fine on most of the flash memory parts. But it doesn't work so well on
parts with internal oscillators; there, it's actually important to
control Vdd.

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2002\05\18@145238 by uter van ooijen & floortje hanneman

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> I believe that to reliably program parts with internal oscillators, your
> programmer design has to be able to control Vcc as well as Vpp (for high
> voltage programming) or RBn/PGM (for low voltage programming, where n=3
> for the 16F87x, 4 for the 16F62x, or 5 for the 18Fxxx). The idea is that
> you avoid powering up the part until you're ready to program it; you
> have to raise both simultaneously or nearly so, so that the program on
> the chip doesn't start running before you get it into programming mode.
> (Unless you have disabled the power-on reset timer, you have 72
> milliseconds before the code starts to run.)

Am I missing a point here? My ICSP programmer talkes its power from the
target cicruit, so it has no means whatsoever to control it. It just pulls
/MCLR low, and then *quickly* rises it to +13V. No problem whatsoever.

Wouter van Ooijen
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Van Ooijen Technische Informatica: http://www.voti.nl
Jal compiler, Wisp programmer, WLoader bootloader, PICs kopen

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2002\05\18@175536 by Peter L. Peres

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On Sat, 18 May 2002, wouter van ooijen & floortje hanneman wrote:

>> I believe that to reliably program parts with internal oscillators, your
>> programmer design has to be able to control Vcc as well as Vpp (for high
>> voltage programming) or RBn/PGM (for low voltage programming, where n=3
>> for the 16F87x, 4 for the 16F62x, or 5 for the 18Fxxx). The idea is that
>> you avoid powering up the part until you're ready to program it; you
>> have to raise both simultaneously or nearly so, so that the program on
>> the chip doesn't start running before you get it into programming mode.
>> (Unless you have disabled the power-on reset timer, you have 72
>> milliseconds before the code starts to run.)
>
>Am I missing a point here? My ICSP programmer talkes its power from the
>target cicruit, so it has no means whatsoever to control it. It just pulls
>/MCLR low, and then *quickly* rises it to +13V. No problem whatsoever.

Until corrected I'll state that the programming mode is entered by pulling
/MCLR from GND (or < 0.4V) to Vpp within the specified short time. Of
course Vdd needs to be supplied first, but it does not matter whether it
was turned on just now or hours ago. I always add a 1N4148 diode with A to
OSC1 and K to /MCLR. It stops the clock when you or the ICSP reset the PIC
and it helps to keep the /MCLR high if you use a strange pullup resistor.
This is only used for development and testing but it has never failed me.
The stopped clock together with the PWRT buy enough time for slower ICSP
programmers to drive the /MCLR. Or so my theory goes (I use a heavily
modified Microchip datasheet (AN577?) type programmer for all
development).

Peter

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