Whilst playing you can either 'Pause' the game by pressing 'start' to access the 'Menu' options or you can go into 'Journal' by pressing back. Enter the codes in the Journal and the screen will flash to confirm correct entry. The directions are done on the D-pad.
Infinite Spell Soul Energy:
Left, Right, Right, Left, Left, Right, Right, Left, Y, Y
Big Demon Heads:
Black, Left, Right, Left, Left, Right, Left, Black
Shoot Large Fireballs:
Y, Y, Y, Left, Right, Right, Left, Left, Right

Rapid Fire Shotgun:
White, Left, Black, Left, Y, X, Y, X

Explosive Holy Bombs:
Right, Left, X, Y, X,Y, Left, Right
Big Weapon Mode:
Left, X, X, X, Y, Y, Y