If you want to use the MPC as the Controller here's what you do....
MIDI plug MPC Midi Out A ----> TRinity MIDI in
Choose the MIDI/SYNC function on the MPC. Select "MIDI OUT A" on the first blank.
Hit the Main window button.
Go down to the "Drums" blank.
Select "MIDI 1"
You might have to set the Trinity to receive messages ... check the manual for that....

peace,
chronos