Intel MCS48 User Manual page 340

8259A
A
D,
C C D,
D
3
Dj
°1
D„
'
M7 M6 M5
M4 M3 M2 Ml MO
INTERRUPT
MASK
t
MASK
SET
=
MASK RESET
R SEOI
EOI
I
I
L, L, L„
BCD LEVEL TO
BE
RESET
OR PUT INTO LOWEST PRIORITY
1
2 3
4
5 6 7
1 1 1 1
1 1 1 1
1 1 t 1
NON
SPECIFIC EOI
SPECIFIC EOI, L0-L2
CODE OF
IS
FF TO BE RESET
ROTATE AT
EOI
AUTOMATICALLY {MODE
A)
ROTATE
AT EOI
(MODE
Bl.
(L0-L2
DEFINES NEW LOWEST PRIORITY)
SET ROTATE
A FF
CLEAR ROTATE A FF
ROTATE PRIORITY (MODE
B)
INDEPENDENTLY OF
EOI
IL0-L2CODE OF
LINE)
NO OPERATION
1
1
1
1
1
1
1
1
1
c
1 1
1
°
\
D, D
6
Dj D
4
3
D, O,
Dj
- ESMM SMM
1
P
ERIS
RIS
READ
IN
SERVICE REGISTER
READ
IR
REG
ON
NEXT
RD PULSE
READ
IS
REG
ON NEXT
RD PULSE
A HIGH ENABLES THE NEXT RD
PULSE
TO READ THE BCD
CODE OF THE HIGH
EST
LEVEL REQUESTING INTERRUPT
SPECIAL MASK MOOE
RESET
SPECIAL
MASK
Operation
Command
Word Format
8-50