Power down mode and Idle mode in 8051

[ucsam]

hello!
I want my 8051 to go to idle mode but i don't know what are the advantages over power down mode,
Can you please show me the advantage ( and actual meaning of it! though i went through the datasheet i still cannot get the whole figure) and how to implement it?
I am using KEIL C

 

[FvM]

The power saving modes are entered by setting bits in the PCON register. I don't know what should be said about these modes other than retelling the data sheet text, which you already know, apparently. I guess, you noticed the difference between both modes regarding peripheral operation and interrupts, otherwise, you should read it more thoroughly.

 

[srizbf]

in the idle mode , by setting IDL bit in PCON ,
it makes the processor in idle state .
In this state, clock signal is available to all peripherals but not to CPU.

an interrupt can resume the idle state to normal state and cpu start executing where it left.

in the PowerDown mode , clock is gated off to all sections including the peripherals. when put in powerdown mode , the supply voltage can be reduced to 2v to keep the internal ram intact.
To comeout of powerdown mode , a hardware reset should be applied.
when comingout from pd mode at hw rest , cpu can execute where it left.

during those modes of idle and power down all state of internal periherals are maintained .

advantage---power consumption.

idle:approx--6mA.
powerdown: approx--40microampere.

 

[ucsam]

the part that confused me is "What will happen to the system if we don't provide clock to CPU?" since, we need reset to comeout of power down mode i prefer to use idle mode.

can u please help me how can i initialize idle mode in Keil C?

 

[FvM]

PCON |= 1; // Set IDL bit in PCON

 

[ucsam]

how do i resume from idle mode?? :???:

 

[FvM]

Raise an (enabled) interrupt or reset the chip.

 

[ucsam]

which interrupt? edge triggered or level triggered? I tried doing both of them but both doesn't work! :|

 

[FvM]

The 8051 documents says any enabled interrupt. I can't give additional hints in this regard. Perhaps you didn't enable the interrupt correctly.

 

[ucsam]

i did! but my system just doesn't resumes. The data sheet says its a level triggred but my sys still doesnt resume!