( -- n )
: _idle 0xff _sdcSR ;

( -- n )
( _sdcSR 0xff until the response is something else than 0xff
  for a maximum of 20 times. Returns 0xff if no response. )
: _wait
    0  ( cnt )
    BEGIN
        _idle
        DUP 0xff = IF DROP ELSE SWAP DROP EXIT THEN
        1+
    DUP 20 = UNTIL
    DROP 0xff
;
375 386 LOADR