You cannot use TTN6 maps with TTN5 application, to be honest the TTN6 maps are so out of date I would save your money, TTN7 is available BUT will only run on specific intended devices.
Consider getting McGuider or Sygic for your PDA as these use latest maps and will work fine with your hardware, they are also very similar in use to TomTom in terms of menu structure/ options etc - Mike |