
382 THE x86 MICROPROCESSORS
D
0
indicates whether ICW4 is necessary.
D
1
indicates whether the system is operating in a slave or master mode. If D = 1, it is a slave
mode and hence ICW3 is not needed.
D
2
= 0 always for the x86 processor.
D
3
selects the options of edge or level triggering for the interrupt lines IR0 to IR7.
D
4
is high always in the ICW1 and D
5
to D
7
is low for x86 processors.
10.3.7.2 | ICW2 (Initialization Command Word2)
is word allows us to decide the type of numbers to be associated with the interrupt input lines
of IR0 to IR7 (See Fig 10.25).
is word is sent with A0 = 1. e bits D
2
to D
0
vary from 000 to 111, and together with ...