VC8E "DONE" flag is cleared by:
  CLEAR on the bus or a DICL IOT.
  ERASE in progress.
  Color change (DILE) in progress.
  DILX or DILY (move) IOT.
  DIXY (intensify) IOT.
  DICD (clear done) IOT.

VC8E "DONE" is set by the last positive edge of:
  LD_DEL since the last DILX or DILY IOT.
  RED_DELAY and GREEN_DELAY have ended.
  SET_DONE interval after erase_interval has ended.
  DEL_1 interval after DIXY (intensify) IOT.

IOT values:
  6050	DILC	Logic Clear
  6051	DICD	Clear Done
  6052	DISD	Skip Done
  6053	DILX	Load X
  6054	DILY	Load Y
  6055	DIXY	Intensify (X, Y)
  6056	DILE	Load Enable
  6056	DILE	Read Enable

Enable Bits:
  0	Done
  1-5	Ignored
  6	Write-Thru
  7	Store
  8	Erase
  9	Color
  10	Channel
  11	Interrupt Enable