Nintendo 1504166 Programming Manual - Page 91
Sound 2, SOUND2CNT_L [d10 - 08] Number of Envelope Steps
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AGB Programming Manual Sound 10.4 Sound 2 Sound 2 is a circuit that generates rectangular waveforms with envelope functions. The contents of NR21, NR22, NR23, NR24 for Sound 2, conform with those of CGB. Address 068h Register SOUND2 CNT_L 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 Attributes Initial Value NR22 NR21 R/W 0000h Sound Length 0-63 Waveform Duty Cycle No. of Envelope Steps 0-7 Envelope Increase/Decrease 0: Attenuate 1: Amplify Envelope Initial-Value SOUND2CNT_L [d15 - 12] Envelope Initial-Value Allows specification of any one of 16 levels ranging from maximum to mute. SOUND2CNT_L [d11] Envelope Increase/Decrease Specifies whether volume will increase or decrease. SOUND2CNT_L [d10 - 08] Number of Envelope Steps Sets the length of 1 step of envelope amplification or attenuation. With n signifying the value specified, the length of 1 step (step time) is determined by the following formula. steptime = n × 1 (sec) 64 When n=0, the envelope function is turned off. SOUND2CNT_L [d07 - 06] Waveform Duty Cycle Specifies the proportion of waveform amplitude peaks. ©1999 - 2001 Nintendo of America Inc. 91 D.C.N. AGB-06-0001-002B4