Hi!
To use com ports of embedded controllers, you can program them as pc coms, it's the same. So you can take a look at PC serial transmit / receive examples. If you can do this, then the next step is to attach modem.
Is it an AT modem? Or is it a point-to-point connection (2 modems, no protocol for modem handling)? Can you describe the modem name/type?
I'm not familiar with AT commands, and I don't know what you can find of already implemented. But common RS-232 modem (non AT) are easy to use, since they just extend an RS-232 connection, and if you build an application which make your computer communicate with FP-2010 through crossed serial cable, then putting 2 modem in the is transparent.
Hope it helps, let me know before I go on Holydays (in about 2 hours 30 minutes
)!
graziano