midis out into mpcs in a. thats all. then if u want to goto pc then it is mpcs out A to the pcs midi in. Midi is like the old player pianos in the western movies. that shit with the roll of notes tellin the keyobard what to play. So if u think bout it like that u gotta just setup what u want to control what. U can just use program 1 (drum1) and u can use the keyboard to control the pads. It helps to goto programs then Note Assign will say like 37 for pad A if u hit open window on the 37 u goto a screen that has all the pad values. U have to change pad A to 36 then pad 2 to 37 pad 3 to 38, all the way up the pads. then ur keyboard will play the pads in order. (as u go thru it the mpc has all these crazy midi note values like pad 3 is 84 or something, so that means the 84 key on the keyboard will play pad 3, instead of havin it down in the 30s like the rest of the pads.)
If u are trying to use the pc or another midi device like
keyboard =====>mpc=====>other midi device
u have to go to where it says DRUM 1 and turn the data whell to the left and it will go to MIDI

ff then change off to 1a to use the midi devices first channel(there are 16 midi channels on one cable.)