Problems with midi

Hi friends, i want to connect my mpc using MIDI. I have a sb live! i connect:

MIDI IN of SB to MIDI OUT of MPC
MIDI OUT of SB to MIDI IN of MPC

good...when i play a note in the pianolla of cubase, i heard the MPC sounds...but if i play a pad of my mpc, cubase dont receive the midi signal...why???

Thanks

Which MPC are you using....

Im using MPC 2000XL