Nintendo 1504166 Programming Manual - Page 88
frequency, Initial, SOUND1CNT_L [d02 - 00] Number of Sweep Shifts
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AGB Programming Manual Sound SOUND1CNT_L [d02 - 00] Number of Sweep Shifts Specifies the number of sweeps. The frequency data with a single shift are determined according to the following formula, with f(t) signifying the frequency after a shift and f(t-1) the frequency before the shift. f(t) = f (t −1) ± f (t−1) 2n f (0) = Initial frequency data If the addition according to this formula produces a value consisting of more than 11 bits, sound output is stopped and the Sound 1 ON flag (bit 0) of NR52 is reset. With subtraction, if the subtrahend is less than 0, the pre-subtraction value is used. However, if the specified setting is 0, shifting does not occur and the frequency is unchanged. Address Register 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 062h SOUND1 CNT_H NR12 NR11 Attributes R/W Initial Value 0000h Sound Length 0-63 Waveform duty cycle No. of Envelope Steps 0-7 Envelope Increase/Decrease 0: Attenuate 1: Amplify Envelope initial value SOUND1CNT_H [d15 - 12] Envelope Initial-Value Allows specification of any of 16 levels ranging from maximum to mute. SOUND1CNT_H [d11] Envelope Increase/Decrease Specifies whether to increase or decrease the volume. ©1999 - 2001 Nintendo of America Inc. 88 D.C.N. AGB-06-0001-002B4