collapseos/drv/acia.z80
2020-04-11 15:11:36 -04:00

60 lines
1.1 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? )
JRZ, L2 FWR ( end, no, wrong 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,
JRZ, L3 FWR ( end, buffer full )
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,
JRNZ, L4 FWR ( skip )
( end of buffer reached )
( +4 == ACIA( )
ACIA_MEM 4 + LDHL(nn),
( +2 == ACIAW> )
ACIA_MEM 2 + LD(nn)HL,
L4 FSET ( skip )
L3 FSET L2 FSET ( end )
DE POPqq,
HL POPqq,
AF POPqq,
EI,
RETI,