Moblie Videogames.?!?

i baught spyro year of the dragon and twisted metal 2 formatted for the psp 3000 on the playstation network. i want to put some cheats but the game won't let me. is there a way i can put cheats on.?

Suggestion:

Download CW Cheat device if you have custom firmware.it is a homebrew plugin through which you can acces cheats inside the game without having to remember the cheat code