: _  ( srcaddr blkno -- )
    [ SDC_DEVID LITN ] (spie)
    0x58 ( CMD24 ) 0 ROT ( a cmd 0 blkno ) _cmd
    IF _err THEN
    _idle DROP 0xfe (spix) DROP 0 SWAP ( crc a )
    512 0 DO         ( crc a )
        C@+          ( crc a+1 n )
        ROT OVER     ( a n crc n )
        _crc16       ( a n crc )
        SWAP         ( a crc n )
        (spix) DROP  ( a crc )
        SWAP         ( crc a )
    LOOP
    DROP ( crc ) 256 /MOD ( lsb msb )
    (spix) DROP (spix) DROP
    _wait DROP 0 (spie) ;