Hello Tosco,
I've had my Tyros nearly a week so I'm still reading the Manual
It mentions Portamento in various sections so I will quote you what it says.
" The Poly/Mono setting and degree of the Portamento effect(Portamento Time) are pre-programmed for each voice. These can be changed via the Sound Creator function and saved as a User Voice.
Portamento Time can also be adjusted from the Mixing Console.
You can also program the foot pedal to perform this function. You can turn this pedal function on or off for each keyboard part on the Mixing Console display"
I hope this helps
Derek