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'"online" programming a PIC?'
1998\02\21@011235 by Bernd Grunwald

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Hello ...

Does anyone know if and how a pic 16F84, 16C84 or any other can be programmed
while it is working? This means that it should not change the states of the
output pins while it is programmed and then start executing the new programm
with the unchanged pin levels ...
An expencive way would IMHO be to use latches to hold the levels of the
output pins while the pic is programmed and then read these levels in the new
programm and continue with those levels set on the pic's pins and then
"disable" the latches again ...
Is there a better and cheaper way to do what I want?
How do I "restart" the pic after programming? Is changing MCLR enough?

--
CU.
-|-\_ Internet: spam_OUTemboTakeThisOuTspambse.netestate.de
-|+/  PGP key available on request

1998\02\21@123332 by wwl

picon face
On Fri, 20 Feb 1998 20:39:11 +0100, you wrote:

>Hello ...
>
>Does anyone know if and how a pic 16F84, 16C84 or any other can be programmed
>while it is working? This means that it should not change the states of the
>output pins while it is programmed and then start executing the new programm
>with the unchanged pin levels ...
>An expencive way would IMHO be to use latches to hold the levels of the
>output pins while the pic is programmed and then read these levels in the new
>programm and continue with those levels set on the pic's pins and then
>"disable" the latches again ...
>Is there a better and cheaper way to do what I want?
>How do I "restart" the pic after programming? Is changing MCLR enough?
No it can't - you have to reset it, which puts the pins in tri-state
Why would you want to do this ? If you're frequently reprogramming it
in-system, e.g. for different functions at different times, remember
the endurance of the program area is a lot less than the data eeprom
(100-1000).
    ____                                                           ____
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_/ W_/  Hardware & Software design / PCB Design / Consultancy  _/ W_/
/_W_/  Industrial / Computer Peripherals / Hazardous Area      /_W_/

1998\02\23@070900 by paulb

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Bernd Grunwald wrote:

> Does anyone know if and how a pic 16F84, 16C84 or any other can be
> programmed while it is working?

 Well, no, but ...

> Is there a better and cheaper way to do what I want?

 Much better.  Use a tokenised programming language stored in data
EEPROM which threads basic routines in main program space. This is what
Stamp basic does (and the 16C84 can support a quarter-size version of
this).  If more space is required, use an external EEPROM.

 Under these constraints, you can re-program "on the fly" without re-
setting at all.  Even better, you only need a one-wire (serial)
interface to do it, easy if you don't require an acknowledgement,
still possible if you do, or a two-wire (plus ground) interface like the
Stamp is even easier.

 Cheers,
       Paul B.

1998\02\28@011556 by embo

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On Mon, 23 Feb 1998, Paul B. Webster VK2BZC wrote:

Hello Paul B. Webster VK2BZC,

{Quote hidden}

Is there a programming example available?

>   Under these constraints, you can re-program "on the fly" without re-
> setting at all.  Even better, you only need a one-wire (serial)
> interface to do it, easy if you don't require an acknowledgement,
> still possible if you do, or a two-wire (plus ground) interface like the
> Stamp is even easier.

The problem is, that the pic controls the power of a PC (and much more :-) )
that should be used to reprogram the pic (pic software update, without the use
of external hardware). So if the PIC toggles the wrong Pin the whole Power goes
down ... And if only the EEProm would be updated there might still be a bug in
the "basic routines" ... :-(

--
CU.
-|-\_ Internet: embospamKILLspambse.netestate.de
-|+/  PGP key available on request

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