ICSP with MP monitoring

[metal]

Hi,

I m unsure if this will work OK for PICs, what do guys think?

[Old_but_Alive]

depends on whats connected to mclr, PGC, PGD.

I would connect a 10K between the pins and the rest of the cicruit unless they are outputs.

[Sideshow Bob]

This is what you can do if you want to more safe than sorry

[metal]

depends on whats connected to mclr, PGC, PGD.

I would connect a 10K between the pins and the rest of the cicruit unless they are outputs.

Nothing is connected to these pins other than the one I have shown in the 1st post.

[dennis78]

I don't work with PICs (and not plan forever ), but If I remember PICs use about 13V on MCLR pin to enter(or all time during programming) in programming mode.
In this case:

1. reset circuit possible can limit this voltage to Vcc+Vd(due to protection diode or because it exceed absolute maximum voltage ratings conditions if protection diodes not exist)
2.R2 also can limit voltage programming -> you can expect problems during ICSP.

In this situation I will add resistor between \RESET output and MCLR pin on mcu (possible>=10k it depend what is PIC programmer current capability on output for MCLR, maybe 1k is enough?). Maybe this will not work for >10k values in normal reset situation if PIC have internal pull up for MCLR pin, but you must read docs and chose good value.

[h0nk]

Hello,

it seens that the APX8035 has an O.C.-Output.
I would assume that this will work.
But You should check the maximum ratiings of this output.


Best Regards

[dennis78]

O.C. output isn't guarantee that protection diodes don't exist.

Absoulte max ratings for reset output = 6V=Vcc -> possible that circuit have protection diodes is very high

Datasheet isn't precise and full informative

[motox]

Don't put more than 5.5V on the APX output pin without a limiting/protection circuit.

I recommend reading the following application notes when using supervisors with PICs:
 - AN820A System Supervisors in ICSP Architectures
 - TB087 Using Voltage Supervisors with PIC Microcontroller Systems which Implement In-Circuit Serial Programming

I usually put two 10kΩ pull-down resistors on the PGD and PGC lines. Don't use pull-ups here, because most ICD programmers have internal 4.7kΩ pull-down resistors.

[h0nk]

O.C. output isn't guarantee that protection diodes don't exist.

Its not O.C., its O.D.: Open Drain.
A true O.C. would have no problems with the programming voltage.

Use a either a supervisor without clamping or an active high output
together with a npn-bjt.

I had no problems with the usual recommended MCLR-connection.
http://www.sonsivri.to/forum/index.php?action=dlattach;topic=69036.0;attach=32197


Best Regards

[metal]

I see, thank you all, circuit is busted, I presume.