YM2610 registers

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Revision as of 17:24, 29 May 2012 by Hpman (talk | contribs) (Reading)
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SSG part

Selectable EG shapes of the SSG
Address (Z80 port 4) Data (Z80 port 5)
$00
Bit 7 6 5 4 3 2 1 0
Def Fine tune
Channel A
$01
Bit 7 6 5 4 3 2 1 0
Def - Coarse tune
$02
Bit 7 6 5 4 3 2 1 0
Def Fine tune
Channel B
$03
Bit 7 6 5 4 3 2 1 0
Def - Coarse tune
$04
Bit 7 6 5 4 3 2 1 0
Def Fine tune
Channel C
$05
Bit 7 6 5 4 3 2 1 0
Def - Coarse tune
$06
Bit 7 6 5 4 3 2 1 0
Def - Noise tune
Noise channel
$07
Bit 7 6 5 4 3 2 1 0
Def - /EN noise/EN A/EN B/EN C
$08
Bit 7 6 5 4 3 2 1 0
Def - ModeVolume
Channel A
$09
Bit 7 6 5 4 3 2 1 0
Def - ModeVolume
Channel B
$0A
Bit 7 6 5 4 3 2 1 0
Def - ModeVolume
Channel C
$0B
Bit 7 6 5 4 3 2 1 0
Def Volume envelope period fine tune
$0C
Bit 7 6 5 4 3 2 1 0
Def Volume envelope period coarse tune
$0D
Bit 7 6 5 4 3 2 1 0
Def - Volume envelop shape
See diagram.

If 'Mode' = 1, the EG is used instead of the 4bit volume value. f = 8M / (Coarse*256 + Fine) ?

Timers

Address (Z80 port 4) Data (Z80 port 5)
$24
Bit 7 6 5 4 3 2 1 0
Def TA counter load bits 9-2
$25
Bit 7 6 5 4 3 2 1 0
Def - TA counter load bits 1-0
$26
Bit 7 6 5 4 3 2 1 0
Def TB counter load bits 0-7
$27
Bit 7 6 5 4 3 2 1 0
Def CSM Mode 3 slot modeReset TB flagReset TA flagEnable TB IRQEnable TA IRQLoad TBLoad TA
  • TA = Timer A, TB = Timer B
  • Timers will tick until they have reached zero, at which point an IRQ will be generated if enabled. Reading port $04 will show which timer caused it.
  • The actual timer counter registers are not directly accessable. They can be reset to zero or initialised from load registers $24-$26
    • Writing 0 to the load bits in register $27 will reset the timer counter registers to zero
    • Writing 1 to the load bits will copy the respective timer load register to the timer counter. This only works when the timer is at zero.
  • When a timer expires, it is automatically reloaded from the load registers and continues.
  • Timer flag reset refers to the same flags that are read from port $04
  • CSM mode is for automatic key on for operators on the second FM channel when timer A expires?

FM part

ADPCM-A part

'Dump' in register $00 is the key on/off bit. Write 0 to start playing specified channels and write 1 to stop playing.

Address (Z80 port 6) Data (Z80 port 7)
$00
Bit 7 6 5 4 3 2 1 0
Def Dump -CH6 ONCH5 ONCH4 ONCH3 ONCH2 ON CH1 ON
$01
Bit 7 6 5 4 3 2 1 0
Def - Master volume
$08~$0D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def L R-Channel volume
$10~$15 (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 LSB
$18~$1D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's start address/256 MSB
$20~$25 (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 LSB
$28~$2D (one for each channel)
Bit 7 6 5 4 3 2 1 0
Def Sample's stop address/256 MSB

ADPCM-B part

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