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'[PICLIST] In circuit pic programming'
2001\02\01@014853 by dre Domingos F. Souza

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       Just a little question, people...

       Let's suppose I have a PIC in circuit, and I've reserved the pins 13 and 12 to be used ONLY by the In Circuit Programmer. Do I need to shut down the circuit and isolate the inputs of the PIC for programming, or when I raise MCLR to >+12v it stops all the I/O activity of the PIC, preparing it to be programmed?

       Any GOOD site about in circuit programming?


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       spam_OUTxandinhoTakeThisOuTspaminterlink.com.br
       Linux User #85093

--------------8<-------Corte aqui-------8<--------------

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2001\02\01@042445 by uter van ooijen & floortje hanneman

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>         Let's suppose I have a PIC in circuit, and I've reserved the pins
13 and 12 to be used ONLY by the In Circuit Programmer. Do I need to shut
down the circuit and isolate the inputs of the PIC for programming, or when
I raise MCLR to >+12v it stops all the I/O activity of the PIC, preparing it
to be programmed?

I can speak only for a few flash PICs (16x84, 16F877): You can use RB6 and
RB7 any way you want, but the programmer must be able to drive the external
circuit and that (the programmer driving the circuit) should not cause any
secundary problems (boms exploding etc.). The programmer must be able to
drive /MCLR both low (0V) and high (12-14V). Note that some reset circuits
include a diode to Vcc, which prevents /MCLR from being driven high. The
transition from low to high must be quick: within N clock cycles (N can be
found somewhere in the uChip documentation). This is the reason that some
programmers will only do ICSP when the Xtal is removed. For 16F877 only:
check older threads about RB3.

>         Any GOOD site about in circuit programming?
http://www.microchip.com search for the in-circuit serial programming manual, and
check the datasheet and programming manual of your traget chip(s)

Wouter

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2001\02\01@052549 by dre Domingos F. Souza

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>I can speak only for a few flash PICs (16x84, 16F877): You can use RB6 and
>RB7 any way you want, but the programmer must be able to drive the external
>circuit and that (the programmer driving the circuit) should not cause any
>secundary problems (boms exploding etc.). The programmer must be able to
>drive /MCLR both low (0V) and high (12-14V). Note that some reset circuits
>include a diode to Vcc, which prevents /MCLR from being driven high. The
>transition from low to high must be quick: within N clock cycles (N can be
>found somewhere in the uChip documentation). This is the reason that some
>programmers will only do ICSP when the Xtal is removed. For 16F877 only:
>check older threads about RB3.

       Interesting...I'm only interested in the 16F84 ICSP, can I switch the clock in/out with a 4066???


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       .....xandinhoKILLspamspam@spam@interlink.com.br
       Linux User #85093

--------------8<-------Corte aqui-------8<--------------

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2001\02\01@070243 by Roman Black

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Alexandre Domingos F. Souza wrote:
>
> >I can speak only for a few flash PICs (16x84, 16F877): You can use RB6 and
> >RB7 any way you want, but the programmer must be able to drive the external
> >circuit and that (the programmer driving the circuit) should not cause any
> >secundary problems (boms exploding etc.). The programmer must be able to
> >drive /MCLR both low (0V) and high (12-14V). Note that some reset circuits
> >include a diode to Vcc, which prevents /MCLR from being driven high. The
> >transition from low to high must be quick: within N clock cycles (N can be
> >found somewhere in the uChip documentation). This is the reason that some
> >programmers will only do ICSP when the Xtal is removed. For 16F877 only:
> >check older threads about RB3.
>
>         Interesting...I'm only interested in the 16F84 ICSP, can I switch the clock in/out with a 4066???


Alexandre, we do this (it works):

1. Hold MCLR low (PIC in reset)
2. Apply power to PIC circuit (PIC still in reset)
3. Raise MCLR from 0v to 13v. (PIC can now be programmed)

There is no need to switch the clock. :o)
-Roman

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2001\02\01@080644 by uter van ooijen & floortje hanneman

picon face
>         Interesting...I'm only interested in the 16F84 ICSP, can I switch
the clock in/out with a 4066???
I don't understand what you mean, why would you want to switch the clock
(and which clock?)?

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2001\02\01@080848 by uter van ooijen & floortje hanneman

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> 1. Hold MCLR low (PIC in reset)
> 2. Apply power to PIC circuit (PIC still in reset)
> 3. Raise MCLR from 0v to 13v. (PIC can now be programmed)

The power can be on all time, provided that step 3. is quick enough.
Wouter

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2001\02\01@082331 by Bob Ammerman

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>        Just a little question, people...
>
>        Let's suppose I have a PIC in circuit, and I've reserved the pins
13 and 12 to be used ONLY by the In >Circuit Programmer. Do I need to shut
down the circuit and isolate the inputs of the PIC for programming, >or when
I raise MCLR to >+12v it stops all the I/O activity of the PIC, preparing it
to be programmed?

Actually when you pull MCLR low to reset _before_ you bring it up to >+12v
the PIC will go into reset and will float all the I/O pins. I'm should then
stay floated when you drive MCLR to Vpp as long as you do so quickly enough
that the oscillator doesn't get 72 cycles in.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

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2001\02\01@085819 by dre Domingos F. Souza

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>>         Interesting...I'm only interested in the 16F84 ICSP, can I switch
>the clock in/out with a 4066???
>I don't understand what you mean, why would you want to switch the clock
>(and which clock?)?

       The docs says I have to raise mclr faster than 72 (?) clock pulses, or else the pc is changed and strange behaviour can happen. The ICSP datasheet says to ground osc1, but Roman (thanks guy) told an easier way to do this.


--------------8<-------Corte aqui-------8<--------------

       All the best!!!
       Alexandre Souza
       xandinhospamKILLspaminterlink.com.br
       Linux User #85093

--------------8<-------Corte aqui-------8<--------------

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2001\02\01@090547 by uter van ooijen & floortje hanneman

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>         The docs says I have to raise mclr faster than 72 (?) clock
pulses, or else the pc is changed and strange behaviour can happen. The ICSP
datasheet says to ground osc1, but Roman (thanks guy) told an easier way to
do this.

Best: just make sure the rise is quick. /MCLR has a rather high impedance,
so unless there is a capacitor to charge almost any scheme will work. If
there is a capacitor you'd better rework the reset circuit.

Wouter

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2001\02\01@133958 by Nigel Goodwin

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In message <.....3A794F92.751EKILLspamspam.....ezy.net.au>, Roman Black <EraseMEfastvidspam_OUTspamTakeThisOuTEZY.NET.AU>
writes
>>         Interesting...I'm only interested in the 16F84 ICSP, can I switch the
>clock in/out with a 4066???
>
>
>Alexandre, we do this (it works):
>
>1. Hold MCLR low (PIC in reset)
>2. Apply power to PIC circuit (PIC still in reset)
>3. Raise MCLR from 0v to 13v. (PIC can now be programmed)

That's exactly what I'm doing for an in-circuit programming application,
it obviously requires an extra line to hold MCLR low, so I'm taking
advantage of that to add a few extra buttons - 'Run', 'Stop', and
'Reset'. 'Stop' holds MCLR low, and 'Run' releases it to let the PIC
run, 'Reset' pulls MCLR low, waits a short while, then releases it
again.
--

Nigel.

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2001\02\02@030639 by Morgan Olsson

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Bob Ammerman wrote:

>Actually when you pull MCLR low to reset _before_ you bring it up to >+12v
>the PIC will go into reset and will float all the I/O pins. I'm should then
>stay floated when you drive MCLR to Vpp as long as you do so quickly enough
>that the oscillator doesn't get 72 cycles in.

Is this independant of oscillator selection?

I mean, doeas it only work for Xtal/ext osc, or also RC osc or internal osc?
(the latter two without startup delay conter)

/Morgan

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2001\02\04@082639 by brah

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"Alexandre Domingos F. Souza" wrote:
>
>
>
>         Let's suppose I have a PIC in circuit,

For what it's worth, I place a set of 8 IDC male pins on mu PC board.
One pair is gnd
One pair is RB6
One pair is RB7
One pair is MCLR
With my Dontronics programmer, I run a cable from the programming port
on Don's programmer, to the IDC pins on my PC board, and the switch on
Don's programmer puts me in either run mode or program mode.  What
happens is - in program mode the PC board circuitry is isolated from RB6
RB7 MCLR and connected to the programmer.  In run mode, the programmer
is isolated from the same RB6 RB7 MCLR pins, and they are connected to
the PC board circuitry.
Once the PIC is programmed, the cable is removed, and jumpers put across
each pair to put the PIC in run mode permanently (untill jumpers are
removed and programmer cable is installed again)
I find this very useful when I know what the hardware and the board are
going to be, but need to fine tune the program on the PIC.

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