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'Why does the PICs require 12-14V to program?'
1996\11\21@021414 by Kim Runholt

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Could anybody explain to me why the program EEPROM on a 16c84 needs
12-14V to be programmed when the data EEPROM can be written using normal
voltage? It it two different types of EEPROM?


- Kim

Mr. Kim Runholt                 | Student at the Faculty of Engineering and
Finger for PGP public key.      | Science at Aalborg University, Denmark
E-mail: spam_OUTrunholtTakeThisOuTspamcs.auc.dk       | Homepage:  http://www.cs.auc.dk/~runholt

1996\11\21@030515 by Wolfram Liebchen

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At 08:13 21.11.96 +0100, you wrote:
>Could anybody explain to me why the program EEPROM on a 16c84 needs
>12-14V to be programmed when the data EEPROM can be written using normal
>voltage? It it two different types of EEPROM?
>- Kim

Hi Kim,

to my knowledge, the Vpp for 16C84 is only a "logic" signal, so you
would not erratically (re-)program the chip.
The 16C84 has an internal voltage-multiplier for the programming
voltage and draws almost no current from the Vpp-line.

Wolfram



+-----------------------------------------------------+
| Wolfram Liebchen                                    |
| Forschungsinstitut fŸr Optik, TŸbingen, Deutschland |
| .....liebchenKILLspamspam@spam@ffo.fgan.de                         |
+-----------------------------------------------------+

1996\11\22@024759 by Hank Gupton

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Mr. Kim Runholt wrote:

>Could anybody explain to me why the program EEPROM on a 16c84 needs
>12-14V to be programmed when the data EEPROM can be written using normal
>voltage? It it two different types of EEPROM?

 The 16c84 uses the 12-14V for signaling purposes only.  Think of it as a
third voltage state.  Or, a way of multplexing two functions onto one pin.
The part literally draws micro amps at the 12-14V level.  The _real_
programming current is generated internally.

 -- Hank

1996\11\22@051456 by John Payson

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> Could anybody explain to me why the program EEPROM on a 16c84 needs
> 12-14V to be programmed when the data EEPROM can be written using normal
> voltage? It it two different types of EEPROM?

It appears that--at least with the current devices--the 16x84 uses VDD for
all the programming power requirements and it would be probably be trivial
[for Microchip] to modify the design of the chip so as not to require VPP.
There are at least three reasons they have not done so:

[1] The programming-mode entry algorithm, on which /MClr is raised to +12,
   is the same as the other parts; were some other method used to trigger
   programming mode, it would be harder to make a 'universal' programmer
   for the serial-mode parts.

[2] In most target applications, unless in-circuit programming is part of
   the app, there isn't really any way /MClr is going to be raised much
   above VDD; as a result, the programming is immune to glitchies and such.
   If conventional logic levels were sufficient to program the device, it
   may be succeptible to accidental erasure/scrambling.

[3] By making /MClr a three-state input (low, high, very-high) Microchip
   makes it possible to use all the pins on the device (at normal logic
   levels) in any combination, without accidentally triggering program
   mode.  By contrast, some other devices may enter programming mode
   erroneously if some of the so-called "general-purpose" I/O pins happen
   to have the wrong values on power-up.

1996\11\25@070453 by efoc

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Kim Runholt wrote:
>
> Could anybody explain to me why the program EEPROM on a 16c84 needs
> 12-14V to be programmed when the data EEPROM can be written using normal
> voltage? It it two different types of EEPROM?
>
> - Kim
>
> Mr. Kim Runholt                 | Student at the Faculty of Engineering and
> Finger for PGP public key.      | Science at Aalborg University, Denmark
> E-mail: runholtspamKILLspamcs.auc.dk       | Homepage:  http://www.cs.auc.dk/~runholt


Hmmmmmm .... Maybee it's because the same pin is used for memory clear

IE. 0v = mem, Clear +5 = normal operation, +13.5 = programme.

Just a thought


Peter ........
--
==================================
= New Ideas come from those who  =
= didn't know it wasn't possible =
==================================

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