Specifications

Interrupt Controller (8259A)
D7 D6 D5 D4 D3 D2 D1 D0
0001
LTIM
0S1
ICW1
D7 D6 D5 D4 D3 D2 D1 D0
S7 S6 S5 S4 S3 S2 S1 S0
D7 D6 D5 D4 D3 D2 D1 D0
A15 A14 A13 A12 A11 0 0 0
ICW2
ICW3 (Master Device)
NOTE 1: SLAVE ID IS EQUAL TO THE CORRESPONDING MASTER IR INPUT.
NOTE 2: X INDICATES "DON'T CARE."
D7 D6 D5 D4 D3 D2 D1 D0
0 0 0 FNM 1AEOI
ICW4
0 0 0 0 0 ID2 ID1 ID0
D7 D6 D5 D4 D3 D2 D1 D0
ICW3 (Slave Device)
1 - SINGLE
0 - NOT SINGLE
1 - LEVEL TRIGGERED INPUT
0 - EDGE TRIGGERED INPUT
I/O ADDRESS = 20h
1 - IR INPUT HAS A SLAVE
0 - IR INPUT DOES NOT HAVE A
SLAVE
SET BY 8259A
ACCORDING TO INTERRUPT
LEVEL
MOST SIGNIFICANT
BITS OF VECTORING BYTE
I/O ADDRESS = 21h
I/O ADDRESS = 21h
1 - AUTO EOI
0 - NORMAL EOI
1 - FULLY NESTED MODE
0 - NOT FULLY NESTED MODE
I/O ADDRESS = 21h
SLAVE ID(1)
I/O ADDRESS = 21h
03456712
01010110
01001101
00111100
1
1
Figure 12–3. 8259A ICW Formats.
12-13