Nintendo 1504166 Programming Manual - Page 97
Sound 4, SOUND4CNT_L [d10 - 08] Number of Envelope Steps
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AGB Programming Manual Sound 10.6 Sound 4 Sound 4 is a circuit that generates white noise with the envelope function. The contents of NR41, NR42, NR43, and NR44 for Sound 4 conform with those of CGB. Address 078h Register SOUND4 CNT_L 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 Attributes NR42 NR41 R/W Initial Value 0000h No. of Envelope Steps 0-7 Envelope Increase/Decrease 0: Attenuate 1: Amplify Envelope Initial-Value Sound Length 0-63 SOUND4CNT_L [d15 - 12] Envelope Initial-Value Allows specification of any of 16 levels ranging from maximum to mute. SOUND4CNT_L [d11] Envelope Increase/Decrease Specifies whether to increase or decrease the volume. SOUND4CNT_L [d10 - 08] Number of Envelope Steps Sets the length of each step of envelope amplification or attenuation. With n the specified value, the length of 1 step (steptime) is determined by the following formula. steptime = n × 1 (sec) 64 When n = 0, the envelope function is turned off. SOUND4CNT_L [d05 - 00] Sound Length With st signifying the sound length, the length of the output sound is determined by the following formula. time = (64 − st ) × 1 (sec) 256 ©1999 - 2001 Nintendo of America Inc. 97 D.C.N. AGB-06-0001-002B4