collapseos/arch/z80/sms/blk/606

: _zero ( x -- send 0 _data x times )
    ( x ) 0 DO 0 _data LOOP ;

( Each row in ~FNT is a row of the glyph and there is 7 of
them.  We insert a blank one at the end of those 7. For each
row we set, we need to send 3 zero-bytes because each pixel in
the tile is actually 4 bits because it can select among 16
palettes. We use only 2 of them, which is why those bytes
always stay zero. )
: _sfont ( a -- Send font to VDP )
    7 0 DO C@+ _data 3 _zero LOOP DROP
    ( blank row ) 4 _zero ;