NSF driver update sequence

NSF driver update sequence

• Last updated: 2026-04-09

Documents the player update order (ft_music_play) of the NSF driver.

In order:

• Run delayed channels
• Check tempo accumulator to do a row update
  • if counter <= 0:
    • ft_do_row_update
      • frame handling
      • ft_read_channels (foreach channels do:)
        • ft_read_pattern
          • ft_read_note
            • switch case pattern command
              • handle volume commands
              • handle instrument commands
              • handle effect commands
            • ft_push_echo_buffer
            • handle note off
            • handle note release
            • load echo buffer
            • ft_push_echo_buffer
            • handle musical note
        • ft_read_is_done
    • ft_restore_speed
  • else:
    • ft_skip_row_update (jumps to after row update code)
• Decrement tempo accumulator counter
• ft_loop_fx_state
  • Sxx handling
  • delayed transpose/release handling
• ft_loop_channels (foreach channels do:)
  • ft_run_effects (handles the rest of the other effects)
  • ft_run_instrument
  • ft_calc_period
  • Nxy handling
• ft_update_<chip> (foreach chip do:)
  • (register writes)