Re: [Flashforth-devel] Loop at Bootup : Pic18f45k20

[Mikael N. <mik...@fl...>]

Hi Richard.

Based on your analysis of your TX data I am pretty convinced that the 
PROMPT vector in EEPROM is corrupt.

The cold initialization of the vectors is triggered by 0xff in the first 
two EEPROM bytes.
If the contents is not 0xff then whatever data happens to be in the 
PROMPT vector is used as an
execution address. A random address there FF go haywire.

So make sure that your device programmer(pickit etc.) erases the eeprom 
before programming FF into the chip.
Erasing the device will set the eeprom contents to 0xff.

If you download the FF that I updated yesterday, it does not execute the 
PROMPT vector directly at startup.
So there should not be any garbage in the TX.

That allows you to give the EMPTY command in case the EEPROM has some 
corrupt values.
EMPTY will write the correct initialization values into EEPROM.

If it still does not work you may have defect chip.

BR Mikael



On 2018-09-18 13:14, Richard Burden wrote:
> Well, there is no signal on Pin 1 (RX) whatsoever. So it seems the Tx
> data is the result of some kind of program error. I'll have to think
> about this some more. But at present it has me stumped.
> 
> Regards
> Richard
>