82C836 Datasheet, PDF (89/205 Pages) List of Unclassifed Manufacturers – Single-Chip 386sx AT

Interrupt Controller
Programming the Interrupt Controller s
Figure 7-13. OCW2----Address 020H (0A0H) Write Only
B7 B6 B5 B4 B3 B2 B1 B0
________ ________ ________ ________ ________ __________________________
L<2:0> Interrupt Channel Select
0
SI
Select Initialization Mode
EOI Enable Operational Interrupt
SL
Select Operational Function
R
Rotation Function Select
bits: B0-B3 L<2:0>
B3 0
B4 SI
B5 EOI
B6 SL
B7 R
These three bits are internally decoded to select which interrupt
channel is to be affected by the specific command. L<2:0> must be
valid during three of the four specific cycles (see SL).
This bit is zero.
Writing a zero in this bit position takes the interrupt controller out of
initialize mode and writes OCW2 or OCW3.
This bit, in conjunction with R and SL, selects operational function.
Writing a one in this bit position causes a function related to EOI to
occur.
• Nonspecific EOI command when R = 0 and SL = 1 and EOI = 0
• Specific EOI command when R = 0 and SL = 1 and EOI = 1
• Rotate on nonspecific EOI when R = 1 and SL = 0 and EOI = 1
• Rotate on specific EOI when R = 1 and SL = 1 and EOI = 1
This bit, in conjunction with R and EOI, selects operational function.
Writing a one in this bit position causes a specific or immediate
function to occur. All specific commands require L<2:0> to be
valid, except no operation.
• No operation when R = 0 and SL = 1 and EOI = 0.
• Specific EOI command when R = 0 and SL = 1 and EOI = 1.
• Specific rotate command when R = 1 and SL = 1 and EOI = 0.
• Rotate on specific EOI when R = 1 and SL = 1 and EOI = 1.
This bit together with SL and EOI selects operational function.
Writing a one in bit 7 causes one of the rotate functions to be
selected.
• Rotate on auto EOI enable. (Note: This function is disabled by
writing a zero to all three bit positions.) When R = 1 and SL = 0
and EOI = 0.
• Rotate on nonspecific EOI when R = 1 and SL = 0 and EOI = 1.
• Specific roate command when R = 1 and SL = 1 and EOI = 0.
• Rotate on specific EOI when R = 1 and SL = 1 and EOI = 1.
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PRELIMINARY
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