Problem proramming PIC 16F886 with PICKIT2?

[jellis00]

I have had strange programming issues with the 16F88x series and Pickit2 a while back.
Turned out to be the PGM pin (RB3) on the PIC needs to be pulled down to GND with ~10K - page 228 of the datasheet.

Hope this helps

BH_epuk: I went to pg 228 in the 16F88x data sheet and the only thing I find that equates to what you are saying is:
"

4:

RB3 should not be allowed to float if LVPis enabled. An external pull-down deviceshould be used to default the device tonormal operating mode. If RB3 floatshigh, the PIC16F882/883/884/886/887

device will enter Programming mode."

From this quote it appears that what you are saying only applies "if LVP is enabled". I am not enabling LVP so I don't think this applies in my case. In fact, I have RB3 connected to Vcc via a pullup resistor of 10K ohms. Your opinion?

[BH_epuk]

Give it a go with PGM pulled down. I only found this after intermittent programming problems on a project some time ago, now allways keep this pin in a way it can be pulled down (even if it means an extra pad on the PCB).

If the device is new then LVP is enabled - note 5 on P228, but i also suspect if the device is erased is default's back to this.

Edit:

In your case pullde to VCC via 10K, just shorting RB3 to GND while programming would do the trick.

[jellis00]

Finally found the problem. Evidently the 16F886 chip had gone bad. When I replaced it with a new chip everything works fine. Don't understand what caused the chip to fail.
In my next board version, however, I will implement some of your suggestions as far as the PGM pin is concerned.

Thanks for all of your good ideas.
John Ellis