YM2610 registers

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Summary: ...

Timers

See YM2610 timers.

SSG part

See SSG for details on this part's operation.

FM part

See FM for details on this part's operation.

Common FM registers

Address (Z80 port 4) Data (Z80 port 5)
$22
Bit 7 6 5 4 3 2 1 0
Def - OnControl
LFO Frequency
$28
Bit 7 6 5 4 3 2 1 0
Def Slot -Channel
Key On/Off

LFO frequency values are as follows:

  • 0 – 3.98Hz
  • 1 – 5.56Hz
  • 2 – 6.02Hz
  • 3 – 6.37Hz
  • 4 – 6.88Hz
  • 5 – 9.63Hz
  • 6 – 48.1Hz
  • 7 – 72.2Hz

Overall channel registers

The first value listed in the Address column is for channels 1/3; the second is for channels 2/4.

Address (Z80 port 4 or 6) Data (Z80 port 5 or 7)
$A1,$A2
Bit 7 6 5 4 3 2 1 0
Def F-Num 1
F-Numbers and Block (1/2)
$A5,$A6
Bit 7 6 5 4 3 2 1 0
Def - BlockF-Num 2
F-Numbers and Block (2/2)
(must set this first)
$A9,$AA
Bit 7 6 5 4 3 2 1 0
Def 2CH * F-Num 1
2CH - 2 Slot F-Numbers/Block (1/2)
$AD,$AE
Bit 7 6 5 4 3 2 1 0
Def - 2CH * Block2CH * F-Num 2
2CH - 2 Slot F-Numbers/Block (1/2)
(must set this first)
$B1,$B2
Bit 7 6 5 4 3 2 1 0
Def - FBALGO
Feedback (FB) and Algorithm (ALGO)
$B5,B6
Bit 7 6 5 4 3 2 1 0
Def L RAMS-PMS
Left (L)/Right (R) output, AM Sense (AMS), and PM Sense (PMS)

Channel registers

Depending on which channel you want to write to, the ports used are different:

  • Channels 1 & 2: Ports 4/5
  • Channels 3 & 4: Ports 6/7

Per-operator registers

The ranges given for the address represent all of the parameter values. Each channel's operators are laid out as follows:

Operator 1 2 3 4
Channels 1, 3 $x1 $x5 $x9 $xD
Channels 2, 4 $x2 $x6 $xA $xE
Address (Z80 port 4 or 6) Data (Z80 port 5 or 7)  
$31-$3E
Bit 7 6 5 4 3 2 1 0
Def - DTMUL
Detune (DT) and Multiple (MUL)
$41-$4E
Bit 7 6 5 4 3 2 1 0
Def - Total Level
Total Level (Volume)
$51-$5E
Bit 7 6 5 4 3 2 1 0
Def KS -AR
Key Scale (KS) and Attack Rate (AR)
$61-$6E
Bit 7 6 5 4 3 2 1 0
Def AM -DR
AM On (AM) and Decay Rate (DR)
$71-$7E
Bit 7 6 5 4 3 2 1 0
Def - SR
Sustain Rate (SR)
$81-$8E
Bit 7 6 5 4 3 2 1 0
Def SL RR
Sustain Level (SL) and Release Rate (RR)
$91-$9E
Bit 7 6 5 4 3 2 1 0
Def - SSG-EG
SSG-EG

ADPCM part

See ADPCM for details on this part's operation.

Address (Z80 port 4) Data (Z80 port 5) Value on reset
$1C
Bit 7 6 5 4 3 2 1 0
Def B -A6A5A4A3A2A1
$00
  • Write to flag control to reset/mask channel end flags
    • Write 1 to reset and/or mask selected flag
    • Write 0 to unmask selected flag
    • Masking a flag will prevent it from being raised when a channel reaches its end address. This means you have to write 1 to clear the flag, then 0 to keep it active.
    • Flags must be manually cleared, playing a new sample on the channel won't clear it.

ADPCM-A part

See ADPCM for details on this part's operation.

Address (Z80 port 6) Data (Z80 port 7) Value on reset
$00
Bit 7 6 5 4 3 2 1 0
Def Dump -CH6 ONCH5 ONCH4 ONCH3 ONCH2 ON CH1 ON
$00 'Dump' is the key on/off bit. Write 0 to start playing specified channels and write 1 to stop playing.
$01
Bit 7 6 5 4 3 2 1 0
Def - Master volume
$00 Actually an attenuator, 0 is the loudest.
$08~$0D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def L R-Channel volume
$00 Actually an attenuator, 0 is the loudest. L/R routes the output to the left and/or right channels.
$10~$15 (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 LSB
$00 All ADPCM addresses must match a 256-byte boundary (bits 0~7 = 0)
$18~$1D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 MSB
$00
$20~$25 (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 LSB
$00
$28~$2D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 MSB
$00

ADPCM-B part

See ADPCM for details on this part's operation.

Address (Z80 port 4) Data (Z80 port 5) Value on reset
$10
Bit 7 6 5 4 3 2 1 0
Def Start -Repeat-Reset
$00 Repeat: loop when end address is reached. Reset: clears Start and Repeat.
$11
Bit 7 6 5 4 3 2 1 0
Def L R-
$00 Left/Right channel output
$12
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 LSB
? All ADPCM addresses must match a 256-byte boundary (bits 0~7 = 0)
$13
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 MSB
?
$14
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 LSB
?
$15
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 MSB
?
$19
Bit 7 6 5 4 3 2 1 0
Def Delta-N (L)
? Playback rate is f = 8M / 12 / 12 / (65535 / Delta-N) = 55555 * (Delta-N / 65535) Hz
$1A
Bit 7 6 5 4 3 2 1 0
Def Delta-N (H)
?
$1B
Bit 7 6 5 4 3 2 1 0
Def ADPCM-B channel volume
? Loudest is $FF

Reading

The only writable registers that can also be read are from the SSG. All other ports and addresses return different data.

Z80 port # Data Notes
$04
Bit 7 6 5 4 3 2 1 0
Def Busy -Timer B flagTimer A flag
When a timer expires and IRQ is enabled for the timer, the respective bit is set
$05
Bit 7 6 5 4 3 2 1 0
Def SSG register data
Attempting to read non-SSG registers will fail
$06
Bit 7 6 5 4 3 2 1 0
Def ADPCM-B end -CH6 endCH5 endCH4 endCH3 endCH2 endCH1 end
When a channel has reached the end address and stops, the respective bit is set, unless masked
$07 not implemented Always returns $00