IFNZ, ( buffer full? )
( no, continue )
DE ADDHLd, ( restore ACIAW> )
( buffer not full, let's write )
ACIA_IO INAi,
(HL) A LDrr,
( advance W> )
HL INCd,
ACIAW> LD(n)HL,
DE ACIA) LDdd(n),
DE SUBHLd,
( cont. )