WDT problem 16F74

Hi guys,

Came across a small poblem when trying to set up the WDT in the 16F74. Firstly i enable it in the config word by writing: & _WDT_ON. Then in the option register i assign the prescaler to the WDT with a value of 1:128 by writing 111 to bits 3/1/0.
This then proceeds to build without any problems, as soon as i try to burn the chip it comes up with this error:

ICD0161: Verify failed (MemType = Config, Address = 0x2007, Expected Val = 0x3FB6, Val Read = 0x3FB2)

When i write &_WDT_OFF this error does not happen any more. Does anyone know what is happening here?

Thanks

Are you erasing the chip first. It looks like the config value is not getting erased. Try doing a blank check after doing an erase.

Mike.

Hi Mike,

I just erased the chip then a blank check, and you were right it is not clearing the config word, this is what i get when doing the check:

ICD0161: Verify failed (MemType = Config, Address = 0x2007, Expected Val = 0x3FFF, Val Read = 0x3FB2)
...Device not blank

Cheers

I'm not familiar with the 16F74 and so this may be completely wrong.

I would guess either Vpp is too low or you have a duff chip.

Mike.