In Circuit Serial Programming

Started by Scott Lingerfelt November 12, 2003

I would like to add ICSP to my project! I am going to setup my header as
seen in this link http://www.melabs.com/support/icsp.htm. My question is
that I am using my PortB 6&7 for outputs connected to an ULN2003, can I also
connect to my header for programming without damaging anything? Should I
add some diodes to the circuit? I am using a PIC16F628 which suggest that I
connect PORTB 4 to ground to stop interference. If I have PortB 4 connected
to the same ULN2003 should I jumper this to ground?

Thanks in advance,

**************************************
Scott Lingerfelt

**************************************
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.537 / Virus Database: 332 - Release Date: 11/6/2003




It seems to me that the requirement to ground a pin (PGM) and the
fact that melabs recommends the PIC be powered from a normal source
rather than the programmer could cause an issue. The PIC state must
be one in which the pins are floating before the ground is applied.

I think you might do well to review the Microchip way of doing
things - read the ICSP app notes. I have gone so far as to use a 10
pin cable header (2 columns of 5 rows). There is a shorting plug in
the header for normal operation that connects Vcc and Vdd from the
normal power supply to the PIC. During programming the shorting
plug is removed and a programming cable inserted. This allows the
programmer to control everything about the PIC as it relates to
ICSP. Vcc, Vdd, Pgm, Clock and Data are carried on the programmer
cable. As soon as the programmer powers up the PIC the PGM pin is
floating and the applied ground is acceptable.

Clearly, you can not have the PIC already powered, the pin
initialized as an output and expect to be able to ground it before
the programmer resets the PIC and causes the pin to float.
--- In , "Scott Lingerfelt"
<slingerfelt@c...> wrote:
>
> I would like to add ICSP to my project! I am going to setup
my header as
> seen in this link http://www.melabs.com/support/icsp.htm. My
question is
> that I am using my PortB 6&7 for outputs connected to an ULN2003,
can I also
> connect to my header for programming without damaging anything?
Should I
> add some diodes to the circuit? I am using a PIC16F628 which
suggest that I
> connect PORTB 4 to ground to stop interference. If I have PortB 4
connected
> to the same ULN2003 should I jumper this to ground?
>
> Thanks in advance,
>
> **************************************
> Scott Lingerfelt
> slingerfelt@c...
> **************************************
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.537 / Virus Database: 332 - Release Date: 11/6/2003