Quastion about Energy Detect function in SMAC - MC1321X

[pvi]

Hi
I have qustion about function Energy Detect in SMAC.  
In my project END device most time work without PAN,i.e they permanently have to energy scan for search suitable PAN. When PAN appear it transmit Beacon frame
1 time in 1 second. Therefore END device have to scan minimum 1 second and then sleep some time. When did Energy Detect function finish? How long time does it take? Does this function find beacon frame? It's important for me.
I can do it in another manner. I don't use Energy Detect and  simply turn modem in RX mode for 1 second. If I don't receive any frame it's mean - channel clear. If I receive frame then I can check LinkQuality and some paremetrs of PAN. Then I can select suitable PAN.
What do you think about it? What is method  of scanning more correct?

Vladimir. 
  

Added p/n to subject.

Message Edited by NLFSJ on 2008-01-09 02:43 PM

[RickN]

Hi,

   The MC1321x Reference Manual describes the Energy Detect function as taking 144uS to warm-up the receiver and another 128uS to measure the received power on that channel.   The Energy Detect function is completed when the cca_irq is asserted.   Once you get the cca_irq interrupt, you will need to read the average power detected from the cca_final[] register, and determine if you got something.  If not, you will need to do another Energy Detect function.   Seems like you could perform back to back Energy Detect functions to cover the period of one second and pick up the PAN.  This would not decode the frame, but tell you something was out there on a specific channel. 

  Thanks,

    Rick

[pvi]

I use MC1321X chip.