FUJITSU MB91460 SERIES FR60 - Manual (Page 885)

869
Chapter 42 Sound Generator
3.Registers
reaches the reload value it sets the INT bit. They are intended to reduce the frequency of
interrupts.
The count input of the Tone Pulse counter is connected to the carry-out signal from the
Decrement counter. And when the Tone count register is set to "00", the Tone Pulse counter
sets the INT bit every carry-out from the Decrement counter. Thus the number of
accumulated tone pulses is:
((Decrement Grade register) +1) x ((Tone Count register) +1)
i.e. When the both registers are set to "00", the INT bit is set every tone cycle.