tutorial.25 の履歴(No.1)

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  • 1 (2023-05-27 (土) 19:48:56)
  • 2 (2023-05-28 (日) 20:11:16)

4000060h - SOUND1CNT_L (NR10) - Channel 1 Sweep register (R/W)
  Bit        Expl.
  0-2   R/W  Number of sweep shift      (n=0-7)
  3     R/W  Sweep Frequency Direction  (0=Increase, 1=Decrease)
  4-6   R/W  Sweep Time; units of 7.8ms (0-7, min=7.8ms, max=54.7ms)
  7-15  -    Not used
Sweep is disabled by setting Sweep Time to zero, if so, the direction bit should be set.
The change of frequency (NR13,NR14) at each shift is calculated by the following formula where X(0) is initial freq & X(t-1) is last freq:
  X(t) = X(t-1) +/- X(t-1)/2^n

4000062h - SOUND1CNT_H (NR11, NR12) - Channel 1 Duty/Len/Envelope (R/W)
  Bit        Expl.
  0-5   W    Sound length; units of (64-n)/256s  (0-63)
  6-7   R/W  Wave Pattern Duty                   (0-3, see below)
  8-10  R/W  Envelope Step-Time; units of n/64s  (1-7, 0=No Envelope)
  11    R/W  Envelope Direction                  (0=Decrease, 1=Increase)
  12-15 R/W  Initial Volume of envelope          (1-15, 0=No Sound)
Wave Duty:
  0: 12.5% ( -_______-_______-_______ )
  1: 25%   ( --______--______--______ )
  2: 50%   ( ----____----____----____ ) (normal)
  3: 75%   ( ------__------__------__ )
The Length value is used only if Bit 6 in NR14 is set.

4000064h - SOUND1CNT_X (NR13, NR14) - Channel 1 Frequency/Control (R/W)
  Bit        Expl.
  0-10  W    Frequency; 131072/(2048-n)Hz  (0-2047)
  11-13 -    Not used
  14    R/W  Length Flag  (1=Stop output when length in NR11 expires)
  15    W    Initial      (1=Restart Sound)
  16-31 -    Not used