YM2610 registers

= SSG part =

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

= Timers =


 * 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.

= 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.