Lacobo: I'm a former MFC10 & PSR2000 (which has the same exact midi configiration as the PSR2100) owner and have had a lot of experience using these two units together.

A critically useful feature on your 9000Pro (and on the PSR9000 & Tyros as well) is a dedicated MFC10 template 'Setup & Configuration Page,' which allows you to program (via Yamaha SysEX) & assign MFC10 foot pedal functions from the keyboard. Regretably, both the PSR2000/2100 doesn't include this.

On the PSR2100, you must program & assign foot pedal functions on the MFC10 itself, and because the MFC10 (via the unit itself) doesn't support programming anything beyond basic midi CC (control change) arranger functions (start, stop, variation 1,2,3,4, and fill), you won't be able to assign the plethera of Yamaha specific functions you could with the 9000pro via the dedicated MFC10 page.

I've since sold my MFC10 (along with manual) to SZ member Richard Peck, so perhaps he can provide you with assistance: http://www.synthzone.com/cgi-bin/ubbmisc.cgi?action=getbio&UserName=Richard+Peck

In the meantime, here's a link to another thread on this topic:
http://www.synthzone.com/ubbs/Forum37/HTML/002455.html

Good luck,

Scott