hi all, got another question abt rom loader for dallas 89c420

i dl the 420kit.exe for 89c420.
i am able to invoke and write to it.

but now, i do not understand y i cannot??
psen is low, ea is low and reset is high all check still cannot see the banner come out..wat is the problem?? the chip has a program written to it already..

last time i could still write and clear..or read the status. now cannot...pls help..

thanks