TCCR?A:
  _modify:
    COM?A:
      description: "Compare Output A Mode"
      _write_constraint: enum
    COM?B:
      description: "Compare Output B Mode"
      _write_constraint: enum
    WGM?:
      _write_constraint: enum
  COM??:
    _replace_enum:
      DISCONNECTED:  [0, "Normal port operation, OCix disconnected"]
      MATCH_TOGGLE:  [1, "Toggle OCix on Compare Match (Might depend on WGM)"]
      MATCH_CLEAR:   [2, "Clear OCix on Compare Match (If PWM is enabled, OCix is set at TOP)"]
      MATCH_SET:     [3, "Set OCix on Compare Match (If PWM is enabled, OCix is cleared at TOP)"]
  WGM?:
    _replace_enum:
      NORMAL_TOP:    [0, "Normal, Top: `0xff`, Update: *Immediate*, Flag: *MAX*"]
      PWM_PHASE:     [1, "Phase Correct PWM, Top: `0xff`, Update: *TOP*, Flag: *BOTTOM*"]
      CTC:           [2, "CTC, Top: *OCRA*, Update: *Immediate*, Flag: *MAX*"]
      PWM_FAST:      [3, "Fast PWM, Top: `0xff`, Update: *TOP*, Flag: *MAX*"]

TCCR?B:
  _modify:
    WGM?2:
      description: "Waveform Generation Mode High Bit (Enable Top: *OCRA* for `PWM` modes)"
    FOC??:
      access: write-only
  CS?:
    _replace_enum:
      NO_CLOCK:      [0, "No clock source (Timer/Counter stopped)"]
      DIRECT:        [1, "Running, No Prescaling"]
      PRESCALE_8:    [2, "Running, CLK/8"]
      PRESCALE_64:   [3, "Running, CLK/64"]
      PRESCALE_256:  [4, "Running, CLK/256"]
      PRESCALE_1024: [5, "Running, CLK/1024"]
      EXT_FALLING:   [6, "Running, ExtClk Tx Falling Edge"]
      EXT_RISING:    [7, "Running, ExtClk Tx Rising Edge"]