Fujitsu MB90390 Series Hardware Manual page 566

CHAPTER 25 SOUND GENERATOR
■ Sound Generator Control Register (Upper)
Figure 25.2-3 Configuration of the Sound Generator Control Register (Upper Byte)
bit 15
00005F
H
Reserved
R/W
R/W : Readable and writable
R : Read only
- : Undefined
: Initial value
■ Sound Generator Control Register (SGCR) (Upper) Contents
Table 25.2-2 Function of Each Bit of the Sound Generator Control Register (Upper)
Bit name
bit15 Reserved bit
bit14 to
Undefined
bit10
BUSY:
bit9
Busy bit
DEC:
bit8 Auto-decrement
enable bit
538
14 13 12 11 10 9
- - - - - BUSY DEC
- - - - -
R R/W
This is a reserved bit. Always write "0" to this bit.
This bit indicates whether the Sound Generator is in operation. This bit is set to "1"
upon the ST bit is set to "1". It is reset to "0" when the ST bit is reset to "0" and the
operation is completed at the end of one tone cycle. Any write instructions performed
on this bit has no effect.
The DEC bit is prepared for an automatic de-gradation of the sound in conjunction
with the Decrement Grade register.
If this bit is set to "1", the stored value in the Amplitude Data register is decremented
by 1(one), every time when the Decrement counter counts the number of tone pulses
from the toggle flip-flop specified by the Decrement Grade register.
8
SGCR (upper)
Initial value
0 X X X X X 0 0
B
bit 8
DEC
0 Auto-decrement disabled
1 Auto-decrement enabled
bit 9
BUSY
0 Operation completed
1 Generator is busy
bit 15
Reserved
0
always write "0" to this bit
1
Function
−
Auto-decrement enable bit
Nusy bit
Reserved bit