mpc555 internal flash programming

Hi,
I am working with mpc555 with Greenhills C compiler. On my board i 
have pulled /RSTCONF to high, i.e hard reset configuration word is 
being read as default 0x00000000. 
I need to write into internal flash of mpc555. For that bit 20 of hard 
reset configuration word should be 1 ie. FLEN should be set.

How can i achieve this with this configuration?

Or the only option in this case is making /RSTCONF as low and read the 
hard reset configuration word from the data lines. Here i will need to 
pull down all the data lines except D20 which i will need to pull up.