PWT and PWL relation

[emersonv6]

Hi,

I've playing for a while with the buzzer & PWT registers and I'm able to
hear 'sound' according to the frequencies supported. The thing I can't
not understand well is the relation between the PWT (pulse width tones)
and the PWL (pulse width light), if exists:

A) After loading some frequency into the PWT, set the volume and hear
the it, if I change PWT to BU in the ASIC_CONF_REG, backlight intensity
changes and sound stops.

B) With LT output selected in the ASIC_CONF_REG instead of PWL, changes
over the PWT registers produce nothing.