Intel 80C186EA User Manual page 163

CLOCK GENERATION AND POWER MANAGEMENT
$mod186
name
;FUNCTION:
;
;
; SYNTAX:
; INPUTS:
;
; OUTPUTS:
; NOTE:
;
PWRSAV
RFTIME
RFCON
PSEN
data
FreqTable
data
lib_80C186
_power_save
_divisor
_power_save
lib_80C186
Example 5-2. Initializing the Power Management Unit for Power-Save Mode
5-22
example_PSU_code
This function reduces CPU power consumption
by dividing the CPU operating frequency by a
divisor.
extern void far power_save(int divisor);
divisor - This variable represents F0, F1 and F2
of PWRSAV.
None
Parameters are passed on the stack as required
by high-level languages
equ xxxxH
equ xxxxH
equ xxxxH
equ 8000H
segment public 'data'
dw 1, 4, 8, 16, 32, 64, 0, 0
ends
segment public 'code'
assume cs:lib_80C186, ds:data
public _power_save
proc far
push bp
mov bp, sp
push ax
push dx
equ word ptr[bp+6]
mov dx, RFTIME
in ax, dx
and ax, 01ffh
div FreqTable[_divisor]
out dx, ax
mov dx, PWRSAV
mov ax, _divisor
and ax, 7
or ax, PSEN
out dx, ax
pop dx
pop bx
pop ax
pop bp
ret
endp
ends
end
;substitute register offset
;Power-Save Register
;Refresh Interval Count
;Register
;Refresh Control Register
;Power-Save enable bit
;save caller's bp
;get current top of stack
;save registers that will
;be modified
;get parameter off the
;stack
;get current DRAM refresh
;rate
;mask off unwanted bits
;divide refresh rate
;by _divisor
;set new refresh rate
;select Power-Save Register
;get divisor
;mask off unwanted bits
;set enable bit
;divide frequency
;restore saved registers
;restore caller's bp