Hello,
I had another issue regarding programming of FXth8705D, The problem was that everytime I try to detect or Program the ic, It always throws some error like this,

Now, After Scratching my head all day started reading datasheet more carefully, and Then I came to this section of the datasheet.

In very first bullet it says, In order to enter into BDM, BKGD should hold down while powering up the FXTH87xx. and My Programmer doesn't have the software control over powering up the target.
What was I doing Wrong?
I inserted all four connector RST, GND, VCC, BKGD, simultaneously which somehow doesn't let FXTH87xx entering into BD mode. What I did was, I connected RST, GND, BKGD first then after that VCC. Which Ensured the First point in the bullet, in above image. and Voila.............I Succeed.
Hope It will help someone, and might save his day.
Thanks and Regards
Sumir Kumar Jha, India