Fujitsu MB96300 series Hardware Manual page 725

MB96300 Super Series Hardware Manual
28.2.4 Tone Count Register (SGTRn)
The Tone Count Register (SGTRn) stores the reload value for the Tone Pulse counter. The
Tone Pulse counter accumulates the number of tone pulses (or number of decrement
operations) and when it reaches the reload value it sets the INT bit, reducing the
frequency of interrupts by the number of programmed tones. The register value is
reloaded into the counter at Tone Pulse counter underflow, Decrement counter
underflow, and falling edge of tone signal.
■ Tone Count Register (SGTRn)
The count input of the Tone Pulse counter is connected to the carry-out signal from the Decrement counter.
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 both registers are set to "00", the INT bit is set every tone cycle.
D7 D6 D5 D4 D3 D2 D1 D0
R/W R/W R/W R/W R/W R/W R/W R/W
CHAPTER 28 SOUND GENERATOR
SGTR
Initial value
X X X X X X X X
B
717