Graham:
        Yes it will erase the osccal value.  You need to read this value before
you erase the part. (Read the "blank" part, and osccal will be in memory
location 0x3ff).  You can put it back by adding this snippet to your
program.

org     0x3ff   ;last memory location
movlw   value   ;load w with osccal value

Jeff Webster
Chance favors the prepared mind

Graham North wrote:
>
> If I erase a 509 JW will the location containing the osc value also be
> erased?
>
> If so how do I put back the defalt value?
>
> I am using MPLAB and PICSTART Plus programmer.
>
> Thanks
>
> GRAHAM