collapseos/drv/acia.z80
2020-04-16 08:18:55 -04:00

61 lines
1.3 KiB
Z80 Assembly

( Save ACIA conf )
ACIA_CTL
: ACIA_CTL [ LITN ] ;
ACIA_IO
: ACIA_IO [ LITN ] ;
ACIA_MEM
: ACIA_MEM [ LITN ] ;
( Memory layout
+0 ACIAR>
+2 ACIAW>
+4 ACIA(
+6 ACIA)
)
(xentry) ~ACIA
AF PUSHqq,
HL PUSHqq,
DE PUSHqq,
( Read our character from ACIA into our BUFIDX )
ACIA_CTL INAn,
0x01 ANDn, ( is ACIA rcv buf full? )
IFNZ,
( correct interrupt cause )
( +2 == ACIAW> )
ACIA_MEM 2+ LDHL(nn),
( is it == to ACIAR>? )
( +0 == ACIAR> )
DE ACIA_MEM LDdd(nn),
( carry cleared from ANDn above )
DE SBCHLss,
IFNZ, ( buffer full? )
( no, continue )
DE ADDHLss, ( restore ACIAW> )
( buffer not full, let's write )
ACIA_IO INAn,
(HL) A LDrr,
( advance W> )
HL INCss,
( +2 == ACIAW> )
ACIA_MEM 2+ LD(nn)HL,
( +6 == ACIA) )
DE ACIA_MEM 6 + LDdd(nn),
DE SUBHLss,
IFZ, ( end of buffer reached? )
( yes )
( +4 == ACIA( )
ACIA_MEM 4 + LDHL(nn),
( +2 == ACIAW> )
ACIA_MEM 2+ LD(nn)HL,
THEN,
THEN,
THEN,
DE POPqq,
HL POPqq,
AF POPqq,
EI,
RETI,