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'Programmer Power'
1996\11\24@144331 by myke predko

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Hi Folks,

I want to develop my own Programmer (Everybody else is doing it), but I want
to do a couple of things differently.

A big one is, I want to use a AC/DC Wall Adapter (aka "Wall Wart") for power
and another PIC (probably a 16C54) to control and communicate with the host
PC.  Now to simplify it, I want to use the incoming DC (15V) as the Vpp
reference.

Now, when I started looking at controlling the Vpp, I wondered about the
following circuit for Vpp:


 +12V ---------+
               |
               <
               > 10K Current Limiting
               <  Resistor
               >
               |            1401
PIC Output ----+-------------|>|-------- To Programmed Part _MCLR


For Programming, the PIC Output Bit would be set to Input Mode (the
corresponding TRIS Bit = 1).  Otherwise (ie when the PIC is being pulled out
of the socket), TRIS=Bit=0 to drop the line down low and isolated it using
the diode.

I don't think there will be any problems.  According to the Programming
Spec, a max of 200 uAmps is drawn through the _MCLR Bit (which would cause a
2 Volt Drop across the 10K Resistor) and there is a 0.7Volt drop through the
1401 diode.  When the PIC pulls the Line down, there will only be 1.5 mAmp
being sunk.

If I start with 15 Volts, I will loose a max of 2 Volts through the 10K
resistor and 0.7 Volts thru the diode.  This leaves 12.3 Volts for
programming (enough to trip the PIC into programming mode).


Does anybody see any problems with this/reasons why I wouldn't want to
program a PIC using this method?

myke

Today, the commercial sector is advancing computer and communication
technology at a breakneck pace.  In 1992, optical fiber was being installed
within the continental U.S. at rates approaching the speed of sound (if
computed as total miles of fiber divided by the number of seconds in the year).

Aviation Week and Space Technology, October 28, 1996

1996\11\24@164946 by Hank Gupton

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Myke wrote:

>For Programming, the PIC Output Bit would be set to Input Mode (the
>corresponding TRIS Bit = 1).  Otherwise (ie when the PIC is being pulled out
>of the socket), TRIS=Bit=0 to drop the line down low and isolated it using
>the diode.

 This will only work for the 16C84.  All other parts will need a _real_
13V, 50 mA typical source.


>I don't think there will be any problems.  According to the Programming
>Spec, a max of 200 uAmps is drawn through the _MCLR Bit (which would cause a
>2 Volt Drop across the 10K Resistor) and there is a 0.7Volt drop through the
>1401 diode.  When the PIC pulls the Line down, there will only be 1.5 mAmp
>being sunk.

 The voltage tolerance is rather tight.  Two volts of slop based on the
_assumption_ that 200 uA will be drawn may end up applying 15V to ~MCLR,
killing your chip.


>Does anybody see any problems with this/reasons why I wouldn't want to
>program a PIC using this method?

 Try it.  Let us know if it works.

 -- Hank

1996\11\24@191918 by Martin J. Maney

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On Sun, 24 Nov 1996, myke predko wrote:

> Now, when I started looking at controlling the Vpp, I wondered about the
> following circuit for Vpp:
>
>
>   +12V ---------+
>                 |
>                 <
>                 > 10K Current Limiting
>                 <  Resistor
>                 >
>                 |            1401
>  PIC Output ----+-------------|>|-------- To Programmed Part _MCLR
>
>
> For Programming, the PIC Output Bit would be set to Input Mode (the

You're assuming the contorlling PIC is essentially disconnected when the
pin is set to iput, but most (?) of the PIC chips have diodes to ground
and Vc, so this won't work.  Even if you use RA4, which lacks the diode to
Vc, you may or may not get satisfactory results, as the PIC still isn't
rated for operation much above the supply.  So maybe it will work for a
while and then the controlling PIC will flake out - who knows?

Another problem is that Microchip specifies a rather fast risetime for Vpp
when entering programming mode - without checking I might guess it was 1
or 2 microseconds.  With 100K series R you don't need much stray
capacitance to slow down that rising edge to the point of causing
problems, perhaps annoying intermittent ones.

And then, as has been mentioned already, most PICs are spec'd for a much
larger current draw during programming, so this could only work for the
16C84 if it works at all.

> If I start with 15 Volts, I will loose a max of 2 Volts through the 10K
> resistor and 0.7 Volts thru the diode.  This leaves 12.3 Volts for
> programming (enough to trip the PIC into programming mode).

Even if that 15 volts is regulated this is pretty marginal, though again
it may well work most fo the time.  If the 15V is unregulated, then it
won't be 15V most fo the time (but it may still work sometimes - PICs,
like most modern electronics, are capable of performance well beyond the
spec'd limits, at least some of them, at least some of the time).

> Does anybody see any problems with this/reasons why I wouldn't want to
> program a PIC using this method?

Yeah, lots.  :-(  :-)

1996\11\24@210525 by Antti Lukats

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At 02:43 PM 11/24/96 EST, you wrote:
{Quote hidden}

Hi Myke,

first reason: C54 does not have open colletor outputs, what means that
all IO pins _do_ have input protection diodes to VSS _and_ VCC ie maximum
voltage on any IO pin (being tri-stated) will not exceed VCC+.7 ie ~5.7V
and thats not enough to enter into programming mode.

I am not sure if RA4 on 16CXX devices can be used, well it can but it
may not be to the specs on maximum allowed voltage on io pin

antti
-- Silicon Studio Ltd.
-- http://www.sistudio.com

1996\11\25@064754 by efoc

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myke predko wrote:
>
> Hi Folks,
>
> I want to develop my own Programmer (Everybody else is doing it), but I want
> to do a couple of things differently.
>
BIG Snip

Myke.
        Why not use an opto isolator to drive the Vpp pin the source current
of the driving diode is quite small and the speed of switching is more
than fast enough. It's what I used. As for the programming voltahe I
used a LM7812 regulator and placed a Diode in series with the Vref to
ground. this has the effect of raising the OP voltage to about 13.5
volt.

       you can use the same trick for the 5 volt rail and a couple of
buffers/inverters for the programming lines.

       So there you  have it 2 voltage regs,2 optos and one 7404. Your
programmer is complete.


Cheers Peter......

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

1996\11\25@165148 by Bradley, Larry

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Myke, take a look at the web site below. Steve has a nifty PIC
programmer that runs from a PC parallel port. Doesn't use any PICs to
run it. He has a PC program to do the programming, of course.

I built it, and it works like a charm.  Even if you build your won, you
could use Steve's ideas for driving the PIC lines. Basically, he uses a
couple of transistors driven by CMOS logic chips at 5 volts ... same as
the PIC.

http://www.ccc.nottingham.ac.uk/~cczsteve/pic84.html

Larry

{Quote hidden}

1996\11\26@051503 by tefan Ranguelov

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Hi Folks,

>
>I want to develop my own Programmer (Everybody else is doing it), but I want
>to do a couple of things differently.
>
>A big one is, I want to use a AC/DC Wall Adapter (aka "Wall Wart") for power
>and another PIC (probably a 16C54) to control and communicate with the host
>PC.  Now to simplify it, I want to use the incoming DC (15V) as the Vpp
>reference.

I am using an AN589 based PIC programmer, but add some futures:

* An extra LED indicating 13,5V on the output can be VERY helpful for
 troubleshooting

* I use a switching step-up converter 5V -> 13,5V. I got this Idea from
 a German HAM-radio magazine. So I can use a AC/AC Wall Adapter with
 7 - 20 V AC output to power the programmer and the PIC circuit or I
can
 use the +5V from my PIC circuit to power the programmer. Since most of
 my projects have their own power supply, it makes programming easy.

I am using this programmer for 'in-circuit' programming.
After a while, I discovered this problems:

What happens on the programmers outputs, if :
* The programmer is powered, but not connected to the PC
* The programmer is powered and connected to the PC, which is off
* The programmer is powered and connected to a running PC, but the
 programmer Software is not started.

My programmer doesnât solves the last one...

May be you will be able to solve this problems better with your new
programmer. Which PIC types you plan to support and what software are
you
going to use ?

Are there recommended connector and pinout for in-circuit PIC
programming?

St.

--
      _____________________________________________________________
     |                                           _____________     |  
     |  Dipl.-Ing. Stefan M. Ranguelov          /____________/|    |
     |                                          |||||||||||||      |
     |  tel.:        +49 (30) 20 181 251                           |
     |  priv.:       +49 (30) 513 66 23                            |
     |  s-mail:      D-10319 Berlin, Mellenseestr. 39/10           |
     |  ---------------------------------------------------------  |
     |  e-mail:      .....rangueloKILLspamspam@spam@informatik.hu-berlin.de              |
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1996\11\26@113946 by myke predko

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To answer Stefan's Questions:

<snip stuff...>
>I am using this programmer for 'in-circuit' programming.
>After a while, I discovered this problems:
>
>What happens on the programmers outputs, if :
>* The programmer is powered, but not connected to the PC
>* The programmer is powered and connected to the PC, which is off
>* The programmer is powered and connected to a running PC, but the
>  programmer Software is not started.

These are the reasons why I am going to develop my own.  Actually, I wanted
to put the programmer in-circuit, just as you are.

My design point is for the programmer to stand alone and power the prototype
circuit (with a wall-wart - maybe you buy them at "Wal-Mart"?  Sorry...)
with a 7805 (To be able to source at least a couple of hundread mAs).


Actually, my design requirements are:

1.  Provide a socketed PIC for allowing pulling it in and out.  With this, I
wanted the clocking and reset on the card so I don't have to set it up
anywhere else.
2.  Use a ZIF Socket for the PIC (only 18 pin).  This is a big point and the
Augat ZIFs I was able to get have 0.040" wide pins which are too big for
most protoboard sockets.  Actually, right now I am using the ZIF plugged
into an 18 pin DIP socket, plugged into a Protoboard.
3.  Have the socketed PIC Signals available on a 0.100" header so it can be
plugged into a protoboard easily.
4.  Have the socketed PIC assembly provide power to the protoboard.  This is
why I want to plug in a Wall-Wart to provide power.
5.  Allow the socketed PIC to run even if the Host PC isn't up and running.
6.  Allow the PIC to be programmed In the development Circuit.
7.  The programmer should communicate with the PC via a Serial Port, not a
parallel port.
8.  Provide RS-232 TX/RX for a cheap and easy way of providing a
debug/communications port to the PIC.
9.  Support/Program the C61/C71/C84 (all the 18 pin 14 bit PICs).

>My programmer doesn't solves the last one...

So, your three "problems" would be encompassed by my design.

On most RS-232 DIY Programmers, TX is used as a clocking/data signal which
is not acceptable for my design point of wanting to be able to communicate
via RS-232.

I didn't want to go with a parallel port programmer for two reasons.  The
first is, is basically cost - I don't want to get another parallel port for
my PC.

The second should be more obvious;  by using an RS-232 Port, I have a cheap
and easy way of providing a debug interface (I'm using HyperTerminal under
Win/95 which doesn't cost anything and I don't have to write anything on the
PC side).  Up to now, I have been using LEDs to tell me what's going on.
I'm sick of doing that and I thought a direct RS-232 Interface would be
better with english (or at least my version of it) messages coming out of
the program.

I know I still have to write the PC/16C54 Programming/Control Software, but
I don't see it as being a major hardship.

>Are there recommended connector and pinout for in-circuit PIC
>programming?

The 16C54 will have interfaces to RB6, RB7, and _MCLR as well as be able to
control power and the _MCLR Voltage.  As far as I can tell, this is it.
When the PIC is being programmed or it's power is off, I will assert the
external reset line (to make sure nothing is driving the Socketted PIC -
although this will be up to the circuit designer to make sure this is
happening).

myke


{Quote hidden}

Today, the commercial sector is advancing computer and communication
technology at a breakneck pace.  In 1992, optical fiber was being installed
within the continental U.S. at rates approaching the speed of sound (if
computed as total miles of fiber divided by the number of seconds in the year).

Aviation Week and Space Technology, October 28, 1996

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