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CLOCK AND POWER MANAGEMENT UNIT
8.4.3 Powerdown Mode and Idle Mode Considerations
• The “wake-up” signals (INT, NMI, and SMI#) are level-sensitive inputs to the wake-up
circuitry. The active state of any of these inputs prevents the device from entering
powerdown or idle mode.
• The refresh control unit cannot perform DRAM refreshes during powerdown.
• Powerdown mode freezes PSCLK and SERCLK.
• When the device exits powerdown mode, the PWRDOWN signal is synchronized with
CLK2 (at the falling edge of PWRDOWN) so that other devices in the system exit
powerdown at the same internal clock phase as the processor.
• The INTR output of the ICU cannot be masked off to the power management unit using the
CLI instruction. If it is necessary to mask off INTR to the power management unit, all the
interrupt inputs to the 82C59As must be masked. This applies to both powerdown and idle
modes.
8.5 PROGRAMMING CONSIDERATIONS
8.5.1 Clock and Power Management Unit Code Example
This section contains these software routines:
Set_Prescale_Value Sets the clock prescale value.
Enter_Idle_Mode Programs the Intel386 EX processor for idle mode.
Enter_Powerdown_Mode Programs the Intel386 EX processor for powerdown
mode.
Mode_Setting_to_Active Returns the Intel386 EX processor to active mode.
See Appendix C for the included header files.
#include <conio.h>
#include “80386ex.h”
#include “EV386EX.h”
/*****************************************************************************
Set_Prescale_Value:
Description:
This function sets the clock prescale value.
Parameters:
Prescale Prescale value
Returns: Error Codes
E_BAD_VECTOR -- Specified Prescale is invalid
E_OK -- Initialized OK, No error.
Assumptions: