Fujitsu MB90390 Series Hardware Manual page 565

■ Sound Generator Control Register (SGCR) (Lower) Contents
Table 25.2-1 Function of Each Bit of the Sound Control Register (Lower)
Bit name
S1, S0:
bit7, bit6 Operation clock
select bits
TONE:
bit5
Tone output bit
OE2:
bit4 Sound output
enable bit
OE1:
bit3 Amplitude output
enable bit
INTE:
bit2 Interrupt enable
bit
INT:
bit1
Interrupt bit
ST:
bit0
Start bit
These bits specify the clock input signal for the Sound Generator.
S1 S0
0 0
0 1
1 0
1 1
When this bit is set to "1", the SGO signal becomes a simple square-waveform (tone
pulses) from the toggle flip-flop. Otherwise the SGO signal is the mixed (AND logic)
signal of the tone and PWM pulses.
When this bit is set to "1", the external pin is assigned as the SGO output. Otherwise the
pin can be used as a general purpose I/O. To enable the SGO output, the corresponding
bit of the Port Direction register should also be set to "1".
When this bit is set to "1", the external pin is assigned as the SGA output. Otherwise the
pin can be used as a general purpose I/O. To enable the SGA output, the corresponding
bit of the Port Direction register should also be set to "1".
The SGA signal is the PWM pulses from the PWM pulse generator representing the
amplitude of the sound.
This bit enables the interrupt signal of the Sound Generator. When this bit is "1" and the
INT bit is set to "1", the Sound Generator signals an interrupt.
This bit is set to "1" when the Tone Pulse counter counts the number of the tone pulses
specified by the Tone Count register and Decrement Grade register.
This bit is reset to "0" by writing "0". Writing "1" has no effect and Read-Modify-Write
(RMW) instructions always result in reading "1".
This bit is for starting the operation of the Sound Generator. While this bit is "1", the
Sound Generator perform its operation.
When this bit is reset to "0", the Sound Generator stops its operation at the end of the
current tone cycle. The BUSY bit indicates whether the Sound Generator is fully
stopped.
When this bit is changed from "0" to "1", the value of Frequency Data register,
Amplitude Data register, Decrement Grade register, and Tone Count register is loaded
into each counter.
CHAPTER 25 SOUND GENERATOR
Function
Clock input
Machine clock
1/2 Machine clock
1/4 Machine clock
1/8 Machine clock
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