5-15
CLOCK GENERATION AND POWER MANAGEMENT
Any unmasked interrupt received by the core will return the processor to Active mode. Interrupt
requests pass through the Interrupt Control Unit with an interrupt resolution time for mask and
priority level checking. Then, after 1½ clocks, the core clock begins toggling. It takes an addi-
tional 6 CLKOUT cycles for the core to begin the interrupt vectoring sequence.
After execution of the IRET (interrupt return) instruction in the interrupt service routine, the
CS:IP will point to the instruction following the HALT. Interrupt execution does not modify the
Power Control Register. Unless the programmer intentionally reprograms the register after exit-
ing Idle mode, the processor will re-enter Idle mode at the next HLT instruction.
Like an unmasked interrupt, an NMI will return the core to Active mode from Idle mode. It takes
two CLKOUT cycles to restart the core clock after an NMI occurs. The NMI signal does not need
the mask and priority checks that a maskable interrupt does. This results in a considerable differ-
ence in clock restart time between an NMI and an unmasked interrupt. The core begins the inter-
rupt response six cycles after the core clock restarts when it fetches the NMI vector from location
00008H. NMI does not clear the IDLE bit in the Power Control Register.
Resetting the microprocessor will return the device to Active mode. Unlike interrupts, a reset
clears the Power Control Register. Execution begins as it would following a warm reset (see “Re-
set and Clock Synchronization” on page 5-6).
5.2.1.4 Example Idle Mode Initialization Code
Example 5-1 illustrates programming the Power Control Register and entering Idle mode upon
HLT. The interrupts from the serial port and timers are not masked. Assume that the serial port
connects to a keyboard controller. At every keystroke, the keyboard sends a data byte, and the
processor wakes up to service the interrupt. After acting on the keystroke, the core will go back
into Idle mode. The example excludes the actual keystroke processing.
Содержание 80C186EA
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Страница 2: ...80C186EA 80C188EA Microprocessor User s Manual 1995...
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Страница 20: ...1 Introduction...
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Страница 28: ...2 Overview of the 80C186 Family Architecture...
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Страница 80: ...3 Bus Interface Unit...
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Страница 130: ...4 Peripheral Control Block...
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Страница 140: ...5 ClockGenerationand Power Management...
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Страница 166: ...6 Chip Select Unit...
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Страница 190: ...7 Refresh Control Unit...
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Страница 206: ...8 Interrupt Control Unit...
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Страница 239: ...INTERRUPT CONTROL UNIT 8 32...
Страница 240: ...9 Timer Counter Unit...
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Страница 266: ...10 Direct Memory Access Unit...
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Страница 295: ...DIRECT MEMORY ACCESS UNIT 10 28...
Страница 296: ...11 Math Coprocessing...
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Страница 314: ...12 ONCE Mode...
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Страница 318: ...A 80C186 Instruction Set Additions and Extensions...
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Страница 330: ...B Input Synchronization...
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Страница 334: ...C Instruction Set Descriptions...
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Страница 383: ...INSTRUCTION SET DESCRIPTIONS C 48...
Страница 384: ...D Instruction Set Opcodes and Clock Cycles...
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Страница 408: ...Index...
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