collapseos/arch/z80/sms/blk/622

: (spie) DROP ; ( always enabled )
: (spix) ( x -- x, for port B )
    0 SWAP ( rx tx ) 8 0 DO
        ( send current bit to TRB, TR's output bit )
        DUP 7 I - RSHIFT 1 AND _TRB!
        1 _THB! ( CLK hi )
        ( read into rx ) SWAP 1 LSHIFT _D1@ ( tx rx<< x )
        0 _THB! ( CLK lo )
        ( out bit is the 6th ) 6 RSHIFT 1 AND OR
    SWAP LOOP ( rx tx ) DROP ;