collapseos/arch/z80/sms/blk/613

: _status
    1 _THA! ( output, high/unselected )
    _D1@ 0x3f AND ( low 6 bits are good )
( Start and A are returned when TH is selected, in bits 5 and
  4. Well get them, left-shift them and integrate them to B. )
    0 _THA! ( output, low/selected )
    _D1@ 0x30 AND 2 LSHIFT OR ;