( -- )
( The opposite of sdcWaitResp: we wait until response is 0xff.
  After a successful read or write operation, the card will be
  busy for a while. We need to give it time before interacting
  with it again. Technically, we could continue processing on
  our side while the card it busy, and maybe we will one day,
  but at the moment, I'm having random write errors if I don't
  do this right after a write, so I prefer to stay cautious
  for now. )
: _ready BEGIN _idle 0xff = UNTIL ;
