Nintendo 1504166 Programming Manual - Page 87
Sound 1, SOUND1CNT_L [d03] Sweep Increase/Decrease
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AGB Programming Manual Sound 10.3 Sound 1 Sound 1 is a circuit that generates rectangular waveforms with sweep (frequency change) and envelope (volume change) functions. The contents of NR10, NR11, NR12, NR13, and NR14 for Sound 1, conform with those of CGB. Address 060h Register SOUND1 CNT_L 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 Attributes Intial Value NR10 R/W 0000h No. of sweep shifts 0-7 Sweep Increase/Decrease 0: Addition (increase frequency) 1: Decrease (decrease frequency) Sweep time SOUND1CNT_L [d06 - 04] Sweep Time These bits specify the interval for frequency change. Setting 000 001 010 011 100 101 110 111 (f128=128Hz) Sweep Time Sweep OFF 1/f128 (7.8 ms) 2/f128 (15.6 ms) 3/f128 (23.4 ms) 4/f128 (31.3 ms) 5/f128 (39.1 ms) 6/f128 (46.9 ms) 7/f128 (54.7 ms) SOUND1CNT_L [d03] Sweep Increase/Decrease Specifies whether the frequency increases or decreases. When the sweep function is not used, the increase/decrease flag should be set to 1. ©1999 - 2001 Nintendo of America Inc. 87 D.C.N. AGB-06-0001-002B4