On 03/29/2012 05:02 PM, Uhrheber wrote:
>
> Also I learned that it isn't a good idea to have a #pragma config DEBUG = ON
> statement in the code, because this will permanently lock you out from
> JTAG after
> flashing.
> Can this be circumvented by using a srst at mclr?
>
> Also you should never use #pragma config JTAGEN = OFF, or
> mJTAGPortEnable(DEBUG_JTAGPORT_OFF), but this is pretty obvious.
I was digging a little with this DEVCFG0 bits. First, i was not able to 
program
this JTAGEN  bit. Always read as 1. Can you really program this bit with 
your Pickit3 ?.

Strange, but mplabX behaves accordingly to the data sheet and there is a 
new errata sheet
and  nothing about this.  Perhaps i got a special chip...:)

I also put bit CP (Code protection, bit 28) to 0. This disables debug 
mode, any reset will  time out, target not halted.
But i can erase it.

Bit 0 does nothing related to Jtag. Same behavior when programming it to 0.

Bit 1 disables any access to Jtag. I found no way with  /MCLR to enable 
Jtag again. There is something related to this in
http://ww1.microchip.com/downloads/en/DeviceDoc/61118F.pdf  See 7.4.2. 
Any idea?
I end erasing my chip with a Pickit2 clone and pic32prog.

I suppose that  mJTAGPortEnable(DEBUG_JTAGPORT_OFF) will put JTAGEN bit 
to 0 in CFGCON, and disable Jtag. In this case you can set  /MCLR at 
reset level and erase the chip, if you like. You don't need a running 
cpu to erase the chip.

The only purpose of this Jtag disable is for reusing the pins that uses 
Jtag. That makes me worry a little. Some input can become outputs and 
can drive or sink more current than the max 15mA as stated in data 
sheet. I have 100 ohm resistor in each line, so i think i am save, but 
you?.  I don't mean you should not reuse this pins, but be careful.

Thanks
Salvador

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