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>
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.
B3
B4
0
SI
B5
EOI
B6
SL
B7
R
Figure 7-13.
OCW2----Address 020H (0A0H) Write Only
Interrupt Controller
Programming the Interrupt Controller
I
Chips and Technologies, Inc.
P R E L I M I N A R Y
Revision 3.0
7-13