Powerdown Mode And Idle Mode Considerations; Programming Considerations; Clock And Power Management Unit Code Example - Intel 386 User Manual

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
Enter_Idle_Mode
Enter_Powerdown_Mode
Mode_Setting_to_Active
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
Returns: Error Codes
E_BAD_VECTOR
E_OK
Assumptions:
CLOCK AND POWER MANAGEMENT UNIT
Sets the clock prescale value.
Programs the Intel386 EX processor for idle mode.
Programs the Intel386 EX processor for powerdown
mode.
Returns the Intel386 EX processor to active mode.
Prescale value
-- Specified Prescale is invalid
-- Initialized OK, No error.
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