Using Amber ff in NAMD

Dear all,
 Has anyone used Amber force field in NAMD calculation? I feel a little bit
 confused: When using Charmm in NAMD, we have topology file to build
 structure (generate psf file), and parameter file to do calculation. But
 when goes to Amber, what is the corresponding topology file? And how about
 the format of the tcl or inp file to generate psf file? Which of the
 parameter files is the best for protein-DNA system? (like parm99.dat,
 parm99EP.dat, etc.)
 Thanks a lot for your kind help!