16F676 programming problem

[ardhuru]

I can't figure this one out.

I
@ DEVICE PIC16F676, INTRC_OSC_NOCLKOUT,WDT_ON, PWRT_OFF, MCLR_OFF, BOD_ON,PROTECT_OFF

Internal oscillator and Master clear off is a combination that often does this. You need to use a Vpp-before-Vdd option in your programming software, if it exists. That should cure it, and reclaim all those chips you've tried, which are currently not (re)programmable.

Regards,

Anand

[ardhuru]

Opps; forgot to mention, this wont work if you're using ICSP with an independent target supply. You'll need to put the chip in a socket / breadboard, and connect all ICSP signals *including* the switched Vdd from the programmer.

Anand

[mister_e]

Even if it never happened to me, I would bet on the MCLR_OFF. Some device programmer are a bit fussy on that. Seems Melabs don't recommend it on their website though.

3. Configure MCLR as a RESET pin if possible. The programmer will attempt to reset the target device at the beginning of the programming process. If the MCLR pin is configured as an input, the programmer may have problems putting the chip into program-mode. This is especially problematic if the target has been previously programmed and is using the programming clock or data lines as outputs.

In some situations, there just aren't enough pins to allow the use of a RESET. Your project will require that MCLR be used as an input. This is common on small, 8-pin PIC MCUs. In these cases, it helps to set the clock and data pins to inputs and place a delay at the beginning of your code. This will allow you to cycle power to the part and start the programming process while the pause is executing.

In a PICBASIC PRO program intended for the PIC12F675, you might start with:

TRISIO = $FF ' set all pins to inputs
PAUSE 1000 ' wait a second

This can make reprogramming much easier to accomplish when the programmer has no means to reset the target device