82C836 Datasheet, PDF (88/205 Pages) List of Unclassifed Manufacturers – Single-Chip 386sx AT

s Programming the Interrupt Controller
Interrupt Controller
Operational Command Words
Operational Command Word One (OCW1) is located at address 021H (0A1H) and may
be written any time the controller is in Initialization mode. Operational Command Words
Two and Three (OCW2 and OCW3) are located at address 020H (0A0H). Writing to
address 020H (0A0H) with a zero in bit 4 places the controller in oeprational mode and
loads OCW2 (if data bit 3 = 0) or OCW3 (if data bit 3 = 1).
Figure 7-12. OCW----Address 021H (0A1H) Read/Write
B7 B6 B5 B4 B3 B2 B1 B0
__________________________________________________________________________
M<7:0> Master Register Interrupt
bits: B0-B7 M<7:0>
These bits control the state of the Interrupt Mask Register. Each
Interrupt Request can be masked by writing a one in the appropriate
bit position (M0 controls IR0 etc.) Setting an IMR bit has no effect
on lower priority requests. All IMR bits are cleared by writing
ICW1.
7-1 2 Revision 3.0
PRELIMINARY
Chips and Technologies, Inc.