INTERRUPT CONTROL UNIT
8-12
8.4.1 Interrupt Control Registers
Each interrupt source has its own Interrupt Control register. The Interrupt Control register allows
you to define the behavior of each interrupt source. Figure 8-4 shows the registers for the timers
and DMA channels, Figure 8-5 shows the registers for INT3:2, and Figure 8-6 shows the registers
for INT0 and INT1.
All Interrupt Control registers have a three-bit field (PM2:0) that defines the priority level for the
interrupt source and a mask bit (MSK) that enables or disables the interrupt source. The mask bit
is the same as the one in the Interrupt Mask register. Modifying a bit in either register also mod-
ifies that same bit in the other register.
The Interrupt Control registers for the external interrupt pins also have a bit (LVL) that selects
level-triggered or edge-triggered mode for that interrupt. (See “Edge and Level Triggering” on
page 8-10.)
The Interrupt Control registers for the cascadable external interrupt pins (INT0 and INT1) have
two additional bits to support the external 8259As. The CAS bit enables cascade mode, and the
SFNM bit enables special fully nested mode.
In-Service
2CH
Priority Mask
2AH
Interrupt Mask
28H
Poll Status
26H
Poll
24H
EOI
22H
Table 8-3. Interrupt Control Unit Registers in Master Mode (Continued)
Register Name
Offset Address
Summary of Contents for 80C186EA
Page 1: ...80C186EA 80C188EA Microprocessor User s Manual...
Page 2: ...80C186EA 80C188EA Microprocessor User s Manual 1995...
Page 19: ......
Page 20: ...1 Introduction...
Page 21: ......
Page 28: ...2 Overview of the 80C186 Family Architecture...
Page 29: ......
Page 79: ......
Page 80: ...3 Bus Interface Unit...
Page 81: ......
Page 129: ......
Page 130: ...4 Peripheral Control Block...
Page 131: ......
Page 139: ......
Page 140: ...5 ClockGenerationand Power Management...
Page 141: ......
Page 165: ......
Page 166: ...6 Chip Select Unit...
Page 167: ......
Page 190: ...7 Refresh Control Unit...
Page 191: ......
Page 205: ......
Page 206: ...8 Interrupt Control Unit...
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Page 239: ...INTERRUPT CONTROL UNIT 8 32...
Page 240: ...9 Timer Counter Unit...
Page 241: ......
Page 265: ......
Page 266: ...10 Direct Memory Access Unit...
Page 267: ......
Page 295: ...DIRECT MEMORY ACCESS UNIT 10 28...
Page 296: ...11 Math Coprocessing...
Page 297: ......
Page 314: ...12 ONCE Mode...
Page 315: ......
Page 318: ...A 80C186 Instruction Set Additions and Extensions...
Page 319: ......
Page 330: ...B Input Synchronization...
Page 331: ......
Page 334: ...C Instruction Set Descriptions...
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Page 383: ...INSTRUCTION SET DESCRIPTIONS C 48...
Page 384: ...D Instruction Set Opcodes and Clock Cycles...
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Page 408: ...Index...
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