> 1. How do I have to play a tune so it won't 'change' when I
switch
> oscillation speeds?
>

From Page VMA-4 of the VMU Development Manual

Tcyc in the table is the cycle clock.
To use the sound output capability of VMU, be sure to set the system
clock to the sub-clock (32 KHz).
At other system clock settings, correct sound output may not be
obtained.

The cycle clock is defined as follows.
System clock 32 KHz (Tcyc = 183.0 us)
For information on setting the system clock, please refer to the VMU
Hardware manual.
* Problems when using other system clock settings
Besides the 32 KHz clock, the VMU can use a 600 KHz and 6 MHz system
clock, but when the latter two
are selected, the following problems occur.
* 600KHz When the 600 KHz clock is selected, the output frequency
tolerance will be -50%, +100%,
which will cause a wide ßuctuation in the actual output sound.
* 6MHz When the 6 MHz clock is selected, power consumption will
increase considerably, resulting in a shorter battery life.


Alexander Villagran
VMU Developer