ask help for 2d-fdtd in cylinderical coordinate system

I got a 2d-fdtd code writen in FORTRAN, but there are some problem showed up on the central line(axis of rotation),but I'VE Checked the algorithm about the E/H update and the central line,and there seems no problem . Now I wonder that if the connection boundary condition .
I don't know whether it's right or not . Is there some one could help me on that ,thank yfdtd_cylinder.rarou