8-17
INTERRUPT CONTROL UNIT
Figure 8-8. Interrupt Mask Register
8.4.4
Priority Mask Register
The Priority Mask register (Figure 8-9) contains a three-level field that holds a priority value.
This register allows you to mask interrupts based on their priority levels. Write a priority value
to the PM2:0 field to specify the lowest priority interrupt to be serviced. This disables (masks)
any interrupt source whose priority is lower than the PM2:0 value. After reset, the Priority Mask
register is set to the lowest priority (seven), which enables all interrupts of any priority.
Register Name:
Interrupt Mask Register
Register Mnemonic:
IMASK
Register Function:
Masks individual interrupt sources
Bit
Mnemonic
Bit Name
Reset
State
Function
INT3:0
External
Interrupt
Mask
0000 0
Set a bit to mask (disable) interrupt requests
from the corresponding external interrupt pin.
DMA1:0
DMA
Interrupt
Mask
0
Set to mask (disable) interrupt requests from
the corresponding DMA channel .
TMR
Timer
Interrupt
Mask
0
Set to mask (disable) interrupt requests from
the timers.
NOTE:
Reserved register bits are shown with gray shading. Reserved bits must be written
to a logic zero to ensure compatibility with future Intel products.
A1202-A0
15
0
T
M
R
D
M
A
0
D
M
A
1
I
N
T
0
I
N
T
1
I
N
T
2
I
N
T
3
Summary of Contents for 80C186XL
Page 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Page 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Page 18: ...1 Introduction...
Page 19: ......
Page 27: ......
Page 28: ...2 Overview of the 80C186 Family Architecture...
Page 29: ......
Page 79: ......
Page 80: ...3 Bus Interface Unit...
Page 81: ......
Page 127: ......
Page 128: ...4 Peripheral Control Block...
Page 129: ......
Page 137: ......
Page 138: ...5 ClockGenerationand Power Management...
Page 139: ......
Page 154: ...6 Chip Select Unit...
Page 155: ......
Page 178: ...7 Refresh Control Unit...
Page 179: ......
Page 193: ......
Page 194: ...8 Interrupt Control Unit...
Page 195: ......
Page 227: ......
Page 228: ...9 Timer Counter Unit...
Page 229: ......
Page 253: ......
Page 254: ...10 Direct Memory Access Unit...
Page 255: ......
Page 283: ......
Page 284: ...11 Math Coprocessing...
Page 285: ......
Page 302: ...12 ONCE Mode...
Page 303: ......
Page 306: ...A 80C186 Instruction Set Additions and Extensions...
Page 307: ......
Page 318: ...B Input Synchronization...
Page 319: ......
Page 322: ...C Instruction Set Descriptions...
Page 323: ......
Page 371: ......
Page 372: ...D Instruction Set Opcodes and Clock Cycles...
Page 373: ......
Page 396: ...Index...
Page 397: ......