5-17
CLOCK GENERATION AND POWER MANAGEMENT
5.2.2.1 Entering Powerdown Mode
Powerdown mode is entered by executing the HLT instruction after setting the PWRDN bit in the
Power Control Register (see Figure 5-9 on page 5-12). The HALT cycle turns off both the core
and peripheral clocks and disables the crystal oscillator. See Chapter 3, “Bus Interface Unit,” for
detailed information on HALT bus cycles. Figure 5-12 shows the internal and external wave-
forms during entry into Powerdown mode.
Figure 5-12. Entering Powerdown Mode
During the T2 phase of the HLT instruction, the core generates a signal called Enter_Powerdown.
Enter_Powerdown immediately disables the internal CPU core and peripheral clocks. The pro-
cessor disables the oscillator inverter during the next CLKOUT cycle. If the design uses a crystal
oscillator, the oscillator stops immediately. When CLKIN originates from an external frequency
input (EFI), Powerdown isolates the signal on the CLKIN pin from the internal circuitry. There-
fore, the circuit may drive CLKIN during Powerdown mode, although it will not clock the device.
CLKIN
Internal
Peripheral
Clock
CLKOUT
S2:0
CPU Core
Clock
OSCOUT
ALE
T4 or T1
T1
T2
TI
Halt Cycle
CLKIN toggles
only when
external
frequency
input is used
Indeterminate
011
A1121-0A
Содержание 80C186EA
Страница 1: ...80C186EA 80C188EA Microprocessor User s Manual...
Страница 2: ...80C186EA 80C188EA Microprocessor User s Manual 1995...
Страница 19: ......
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 139: ......
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 205: ......
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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