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'[PIC]: Clock in programming'
2002\01\02@014946 by Alexandre Domingos F. Souza

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       A little question:

       I'm doing a little "prototype lab" for the pic 16F84. Just a NoPPP programmer, with a key to take the programmer off circuit, and a MAX 232 A in the same box, for RS232<>TTL shift. I want to have a little "box" with two cables coming out of that: PIC data lines and TTL from the MAX 232. It will form my "portable devstation" which I can use at my work.

       The little question: Can the cristal/capacitors still be connected while the PIC is being programmed? Or should I take it off while programming?

       Thanks ;o)


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2002\01\02@030619 by uter van ooijen & floortje hanneman

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>         The little question: Can the cristal/capacitors still be connected
while the PIC is being programmed? Or should I take it off while
programming?

Yes, the crystal can inprinciple stay connected, but simple (serial port)
programmers often don't rise the /MCLR fast enough, so in that case the
crystal must be disconnected for succesfull programming. This was a reason
for me to develop my own in-circuit programmer.

Wouter van Ooijen

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2002\01\02@114646 by Roman Black

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Alexandre Domingos F. Souza wrote:
>
>         A little question:
>
>         I'm doing a little "prototype lab" for the pic 16F84. Just a NoPPP programmer, with a key to take the programmer off circuit, and a MAX 232 A in the same box, for RS232<>TTL shift. I want to have a little "box" with two cables coming out of that: PIC data lines and TTL from the MAX 232. It will form my "portable devstation" which I can use at my work.
>
>         The little question: Can the cristal/capacitors still be connected while the PIC is being programmed? Or should I take it off while programming?


Hi Alexandre, yes it will work. The flash PICs
are just held in a typical "reset" state when
programming, ie high impedance ports, etc.
You can have any or all of your circuit attached
to the PIC, it won't matter unless you upset
the programming MCLR, SCL or SDA lines.

I have a little setup like this and it's great.
Flip one switch, program, flip it back, device
is running. Who needs an ICE?? ;o)
-Roman

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2002\01\02@120532 by David VanHorn

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>
>I have a little setup like this and it's great.
>Flip one switch, program, flip it back, device
>is running. Who needs an ICE?? ;o)
>-Roman

I'm doing an AVR project right now, where one AVR reprograms three other
AVRs in circuit, while not letting the peripherals nuke themselves during
that process.   Each AVR, except for the battery charger, has Jtag ICE
ability.  There's also a PIC, but it's running canned firmware, doing IRDA
to serial conversion.   The AVRs all chat over the SPI bus, with a
busreq/busack protocol.

One of them (tiny-15) is a battery charger, doing PWM to regulate the
battery current with one of the lines that is used for programming, and an
analog reference voltage on another programming line (it's an 8 pin part)
so I used a 4066 to gate the signals, with the 4066 toggled on /RESET
I put a further lockout on the PWM output with a transistor, so that if
/RESET is true, then the output FET is disconnected from the CPU, and
biased off.  It would have been bad, to have the battery get a charge
determined by the programming cycle!  :)

Whenever you're going to hold the processor in reset, and have the rest of
the system powered up, you need to pay close attention to what all those
I/O pins are going to do when the processor tri-states them.

A partner of mine once made the mistake of using an ICE in developing an
impact printer.
Not that this is such a bad idea, except that you don't want to place a
breakpoint anywhere when the hammer drivers might be in the "on"
state...  SSSSSmokin!

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2002\01\02@143827 by uter van ooijen & floortje hanneman

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> Hi Alexandre, yes it will work. The flash PICs
> are just held in a typical "reset" state when
> programming, ie high impedance ports, etc.
> You can have any or all of your circuit attached
> to the PIC, it won't matter unless you upset
> the programming MCLR, SCL or SDA lines.

But
- the rise time of the /MCLR is specified in clock cycles
- tie the LVP-enable low

> I have a little setup like this and it's great.
> Flip one switch, program, flip it back, device
> is running. Who needs an ICE?? ;o)

I still prefer my wisp programmer:
- program
- verify (at expremes of vcc if desired)
- run
- communicate (asynch serial)
without touching your target at all!

Wouter van Ooijen

Van Ooijen Technische Informatica: http://www.voti.nl
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2002\01\03@025515 by Alexandre Domingos F. Souza

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       Hi Roman! Happy new year for you! ;oD

>Hi Alexandre, yes it will work. The flash PICs
>are just held in a typical "reset" state when
>programming, ie high impedance ports, etc.
>You can have any or all of your circuit attached
>to the PIC, it won't matter unless you upset
>the programming MCLR, SCL or SDA lines.

       Thanks for the input! I bought a little 6 x 2 key, that will key MCLR, SCL, SDA and 5V in programming. So the clock will stay connected. The little box will have a 5V supply, 12V supply, PIC programmer and level shifter RS232<>TTL. So it will be enough for most of my applications.

>I have a little setup like this and it's great.
>Flip one switch, program, flip it back, device
>is running. Who needs an ICE?? ;o)

       Hehe, nice! Can we share photos and schematics? I'd like to take a look ;o)))

       My old 486 Notebook is turning the ultimate PIC development portable station! ;oD


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2002\01\03@030337 by Alexandre Domingos F. Souza

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>I still prefer my wisp programmer:
>- program
>- verify (at expremes of vcc if desired)
>- run
>- communicate (asynch serial)
>without touching your target at all!

       I'll take a look, Wouter, but I'd like to roll myself ;o) For the sake of learning, of course...


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2002\01\03@072601 by uter van ooijen & floortje hanneman

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> >I still prefer my wisp programmer:
> I'll take a look, Wouter, but I'd like to roll myself ;o) For the sake of
learning, of course...
I could not agree more about the learning aspect, but I just wanted to point
out that you can probably do better than having to flip a switch (relais
controlled by a handshake line?)

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2002\01\04@031734 by Roman Black

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Alexandre Domingos F. Souza wrote:
>
>         Hi Roman! Happy new year for you! ;oD

Thanks! And you too dude. :o)

> >I have a little setup like this and it's great.
> >Flip one switch, program, flip it back, device
> >is running. Who needs an ICE?? ;o)
>
>         Hehe, nice! Can we share photos and schematics? I'd like to take a look ;o)))
>
>         My old 486 Notebook is turning the ultimate PIC development portable station! ;oD


I'll put the photos up on my web page soon, it
needs updating. The schematic is very simple, just
a switch to discnnect the MCLR/SCL/SDA lines, or
just the MCLR will work if you only have a one pole
switch. Then the rest of the box is a large
breadboard setup with leds, buttons, switches etc.

I always add a heap of wires with series resistors to
the PC parallel port via a simple cable and plug.
I can do bidirectional comms with many parallel
bits at quite high speeds. It always amuses me
that people try to implement serial protocols with
MAX chips and stuff. I gave up that years ago and
just connect everything to the PC parallel port,
it's just a couple of octal latches attached to
your pentium chip, and VERY high performance for
such a simple connection system.
-Roman

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2002\01\04@033108 by ards, Justin P

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Roman,
Re LPT port, I was playing with the port and found I could get 8 outputs and
5 inputs.  I read that the 8 outputs could be used as inputs but read is
best not to do this for compatibility issues.  Does this sound true

Justin



{Original Message removed}

2002\01\05@042738 by Alexandre Domingos F. Souza

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>I'll put the photos up on my web page soon, it
>needs updating. The schematic is very simple, just
>a switch to discnnect the MCLR/SCL/SDA lines, or
>just the MCLR will work if you only have a one pole
>switch. Then the rest of the box is a large
>breadboard setup with leds, buttons, switches etc.

       This is the same I did. Just left the crystal connected. I haven't still put it working, but I hope I can get it working tomorrow (today is day of net gamming at my house, some 10 computers connected in a 100 MBit ethernet network, playing Unreal Tournament, hehhe), and finish this thing. It will be nice, ehehehe

{Quote hidden}

       Parallel port IS the way to go, but every type of connection has it's use, even the serial port ;o)


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2002\01\05@082122 by Roman Black

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Alexandre Domingos F. Souza wrote:

>         This is the same I did. Just left the crystal connected. I haven't still put it working, but I hope I can get it working tomorrow (today is day of net gamming at my house, some 10 computers connected in a 100 MBit ethernet network, playing Unreal Tournament, hehhe), and finish this thing. It will be nice, ehehehe

The crystal connected won't matter in ICSP.
Hope you get it fixed up! Have fun net fragging!
-Roman

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2002\01\05@090733 by uter van ooijen & floortje hanneman

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> The crystal connected won't matter in ICSP.

Except that without a crystal (or with a low-frequency crystal) the /MCLR
rise time (from vcc to vpp) is easier to meet, because this rise time is
expressed in osc periods.

Wouter van Ooijen

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2002\01\05@101641 by Roman Black

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Richards, Justin P wrote:
>
> Roman,
> Re LPT port, I was playing with the port and found I could get 8 outputs and
> 5 inputs.  I read that the 8 outputs could be used as inputs but read is
> best not to do this for compatibility issues.  Does this sound true
>
> Justin


Hi Justin, there are actually 3 ports but
some pins are I/O, and some are only dedicated
inputs or outputs. The MAIN port (8 pins)
is bidirectional, has been for many years,
and I prefer to use the dedicated inputs
and outputs for most stuff as you are pretty
much guaranteed compatibility on any PC, even
old ones. And obviously it's good to keep
the main 8bit port available for data use
if you need that.

In most cases you can interface to the port
with just a 220 ohm resistor from each port
pin to your PIC (or any 5v digital) pin. Port
hardware is pretty rugged, i've never fried
a parallel port in years of plugging them
live.

There is some good data on the net, try this:
http://www.beyondlogic.org/spp/parallel.htm
-Roman

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2002\01\06@185220 by Peter L. Peres

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> > The crystal connected won't matter in ICSP.
>
> Except that without a crystal (or with a low-frequency crystal) the
> /MCLR
> rise time (from vcc to vpp) is easier to meet, because this rise time is
> expressed in osc periods.

For which reason I put a normal Si diode with A to OSCin and K to /MCLR in
ICSP-capable designs ... the pwrte timer does the rest (even if off it
takes longer for the crystal to start than the rise time of even the
slowest /MCLR driver).

Peter

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2002\01\07@014503 by dr. Imre Bartfai

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Hi,

AFAIK there is a contradiction. It is completely true what Wouter wrote,
but just in the case of ICSP it does not matter as the oscillator
connected to the PIC does not run. Or am I wrong?

Regards,
Imre

On Sat, 5 Jan 2002, wouter van ooijen & floortje hanneman wrote:

{Quote hidden}

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2002\01\07@165719 by uter van ooijen & floortje hanneman

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> AFAIK there is a contradiction. It is completely true what Wouter wrote,
> but just in the case of ICSP it does not matter as the oscillator
> connected to the PIC does not run. Or am I wrong?

The oscillator may stop when MCLR raise to vpp level, but while MCLR is
above reset level but below vpp level the PIC is simply and plainly in run
mode, it does not yet know that you are attempting to enter programming mode
(because MCLR is not yet that high). When this situation lasts too long
soming goes wrong (I think the PC has started incrementing or something like
that). I know this from experience because along time ago (before wisp,
somewhere in the last century) I used a simple almost-no-parts serial port
programmer for ICSP, and I had to remove the xtal while programming.

Wouter van Ooijen

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