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8xC196EA microcontroller user's manual.1998.pdf
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SPECIAL OPERATING MODES

14.3 IDLE MODE

In idle mode, the microcontroller’s power consumption decreases to approximately 60% of normal consumption. Internal logic holds the CPU clocks at logic zero, causing the CPU to stop executing instructions. Neither the phase-locked loop circuitry, the peripheral clocks, nor CLKOUT is affected. So, the special-function registers (SFRs) and register RAM retain their data; and the peripherals and interrupt system remain active. Table B-5 on page B-15 lists the values of the pins during idle mode.

14.3.1 Enabling and Disabling Idle Mode

The PD bit in the chip configuration register 0 (CCR0.0) either enables or disables both idle and powerdown modes. CCR0 cannot be accessed by code; the PD bit value is defined in chip configuration byte 0 (CCB0.0). If the PD bit is set, both idle and powerdown modes are enabled. If the PD bit is clear, both are disabled. CCR0 is loaded from CCB0 when the microcontroller returns from reset.

14.3.2 Entering and Exiting Idle Mode

The microcontroller enters idle mode after executing the IDLPD #1 instruction. Any enabled interrupt source, either internal or external, or a hardware reset can cause the device to exit idle mode. When an interrupt occurs, the CPU clocks restart and the CPU executes the corresponding interrupt service or PTS routine. When the routine is complete, the CPU fetches and then executes the instruction that follows the IDLPD #1 instruction.

NOTE

To prevent an accidental return to full power, hold the external interrupt pin (EXTINT) low while the device is in idle mode.

14-5

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