issues regarding fpp programming of EP3C40

we are trying fast passive parallel programming the EP3C40 from EP3C16 and DSP processor (BF537)

we are generating the nconfig 600ns of low to high pulse.

in reply EP3C40 generates 60us nstatus signal

we are waiting for 250us before loading the *.rbf file.

we are unable to get the config_done signal high.

is there any necessary points to take care before programming

any suggestions ?