Nintendo GAME BOY Programming Manual page 89

Name Address Bit 7
NR44 FF23
Counter/Continuous Selection:
0: Outputs continuous sound regardless of length data in register NR41.
1: Outputs sound for the duration specified by the length data in register
NR41. When sound output is finished, bit 3 of register NR52, the Sound 4
ON flag, is reset.
Initialize:
Setting this bit to 1 restarts Sound 4.
♦ ♦ ♦ ♦ Sound 4 Usage Notes
When a value is written in the envelope register, the sound output becomes unstable until the initial flag is
set. Hence, set the initial flag immediately after writing a value in the envelope register.
6 5 4 3 2 1 0
R/W(Only the shaded portion
( ) can be read.)
Counter/Continous Selection
Initialize
89
Chapter 3: Sound Functions