Intel 80C186EA, User Manual

Page: 157 / 417

CLOCK GENERATION AND POWER MANAGEMENT
5-16
Example 5-1. Initializing the Power Management Unit for Idle or Powerdown Mode
5.2.2 Powerdown Mode
Powerdown mode freezes the clock to the entire device (core and peripherals) and disables the
crystal oscillator. All internal devices (registers, state machines, etc.) maintain their states as long
as V
CC
is applied. The BIU will not honor DMA, DRAM refresh and HOLD requests in Power-
down mode because the clocks for those functions are off. CLKOUT freezes in a logic high state.
Current consumption in Powerdown mode consists of just transistor leakage (typically less than
100 microamps).
$mod186
name
example_80C186_power_management_code
;FUNCTION: This function reduces CPU power consumption.
; SYNTAX: extern void far power_mgt(int mode);
; INPUTS: mode - 00 -> Active Mode
; 01 -> Powerdown Mode
; 02 -> Idle Mode
; 03 -> Active Mode
; OUTPUTS: None
; NOTE: Parameters are passed on the stack as required
; by high-level languages
PWRCON equ xxxxH ;substitute PWRCON register
;offset
lib_80C186 segment public 'code'
assume cs:lib_80C186
public _power_mgt
_power_mgt proc far
push bp ;save caller's bp
mov bp, sp ;get current top of stack
push ax ;save registers that will
push dx ;be modified
_mode equ word ptr[bp+6] ;get parameter off the
;stack
mov dx, PWRCON ;select Power Control Reg
mov ax, _mode ;get mode
and ax, 3 ;mask off unwanted bits
out dx, ax
hlt ;enter mode
pop dx ;restore saved registers
pop ax
pop bp ;restore caller's bp
ret
_power_mgt endp
lib_80C186 ends
end