Sharp MZ-5500 Tehnical Manual page 38

~
ii) Interrupt proeessing
If the CPU is the Z-80A, the Z- 80A CTC a~tomatieal1y exeeutes the interrupt
aeknowledge eyele and the interrupt
/
the ease of the MZ - 5600, there is a
return cycle by its hardware. But,
need of exeeuting the interrupt ,
in
processing routine by the software. Besides, as the 8259A manages the
intcrrupt of the MZ-5500/5600, the interrupt terminate command (EOI) must
be issued to the 8259A, when it is possible to accept an interrupt of a
higher priority at the end ' of the interrupt processing routine. The
following deseribes the operational flow.
~
....
Interrupt proce66
-'
I
"OV DX,240H
IN ,
Al, DX
~
Dummy, interrupt acknowledge eyele
f
Interrupt
cl,(\nnel
diS
t
i (\
c
t,i
on
I
"OV
"OV
OUT
MOV
OUT
DX.260H
Al,OEOH
DX, AL
Al,4 DH
DX.AL
~
Dummy, interrupt return cycle
. \
I
Jnterrupt process
I ,
"OV Al,20H
~
EOI command
OUT 30H,AL
I
STJ
j
I
,
-....,
I
RET
'­
1ii) Cheeking interrupt ehannel (MZ-5600 only)
The Z-80A CTC
~end~
out the interrupt vector in the
interrupt acknowledge eycle. Since the vector is
set in the AL register when
th~
MZ-5600 executes
the dummy interrupt aeknowledge eyele, the channel
ean be known from the state of the register.
Because the vector "OH" has been set in the CTC-l,
the veetor "08H" must be set in the CTC-2.
Ch
3
Vector
06H
4 08H
5
OAH
6 ' OCH ,
I
7 OEH
l
35