82443MX Datasheet, PDF (134/173 Pages) Intel Corporation – PCIset

82443MX PCIset
ICW 1
I/O Address
CNTRL-1
CNTRL-2
020h
0A0h
Special Conditions
D4 = 1
ICW2
IN CASCADE
MODE?
YES (SNG L=0)
ICW 3
IS IC W 4
NEEDED?
YES (IC 4=1)
ICW 4
021h
0A1h
M ust im m ediately follow
ICW 1 Access
021h
0A1h
M ust im m ediately follow
ICW 2 Access
021h
0A1h
M ust im m ediately follow
ICW 3 Access
READY TO ACCEPT
INTERRUPT REQUESTS
SIO-04.drw
Figure 17. Initialization Sequence for the 440MX ICW Modes of Operation
7.10.1.3.2OPERATION COMMAND WORDS (OCWS)
OCWs are command words that dynamically reprogram the Interrupt Controller to operate in various interrupt
modes. OCWs can be written to the Interrupt Controller any time after initialization. The three Operation
Command Words are referred to by their acronyms: OCW1, OCW2, and OCW3.

Any interrupt lines can be masked by writing an OCW1. A 1 written to any bit of this command word
masks the incoming interrupt requests on the corresponding IRQx line.
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