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CLOCK GENERATION AND POWER MANAGEMENT
$mod186
name
;FUNCTION:
;
SYNTAX:
;
INPUTS:
;
;
;
; OUTPUTS:
;
NOTE:
;
PWRCON equ xxxxH
lib_80C186
_power_mgt
_mode
_power_mgt
lib_80C186
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
is applied. The BIU will not honor DMA, DRAM refresh and HOLD requests in Power-
CC
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).
5-16
example_80C186_power_management_code
This function reduces CPU power consumption.
extern void far power_mgt(int mode);
mode - 00 -> Active Mode
01 -> Powerdown Mode
02 -> Idle Mode
03 -> Active Mode
None
Parameters are passed on the stack as required
by high-level languages
segment public 'code'
assume cs:lib_80C186
public _power_mgt
proc far
push bp
mov
bp, sp
push ax
push dx
equ
word ptr[bp+6]
mov
dx, PWRCON
mov
ax, _mode
and
ax, 3
out
dx, ax
hlt
pop
dx
pop
ax
pop
bp
ret
endp
ends
end
;substitute PWRCON register
;offset
;save caller's bp
;get current top of stack
;save registers that will
;be modified
;get parameter off the
;stack
;select Power Control Reg
;get mode
;mask off unwanted bits
;enter mode
;restore saved registers
;restore caller's bp
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