ATMEGA128RFA1_11 Datasheet, PDF (71/560 Pages) ATMEL Corporation – 8-bit Microcontroller with Low Power 2.4GHz Transceiver for ZigBee and IEEE 802.15.4

ATmega128RFA1
P_RF = -90 + ED [dBm]
Figure 9-18. Mapping between values in PHY_ED_LEVEL and Received Input Power
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
Measured
Ideal
10
20
30
40
50
60
70
80
90
Register PHY_ED_LEVEL Value
9.5.4.4 Interrupt Handling
The TRX24_CCA_ED_DONE interrupt is issued at the end of a manually initiated ED
measurement.
Note that an ED request should only be initiated in one of the receive states. Otherwise
the radio transceiver generates a TRX24_CCA_ED_DONE interrupt but no ED
measurement was performed.
9.5.5 Clear Channel Assessment (CCA)
The main features of the Clear Channel Assessment (CCA) module are:
• All 4 modes are available as defined by IEEE 802.15.4-2006 in section 6.9.9;
• Adjustable threshold for energy detection algorithm.
9.5.5.1 Overview
A CCA measurement is used to detect a clear channel. Four modes are specified by
IEEE 802.15.4-2006:
Table 9-21. CCA Mode Overview
CCA Mode Description
1
Energy above threshold.
CCA shall report a busy medium upon detecting any energy above the ED
threshold.
2
Carrier sense only.
CCA shall report a busy medium only upon the detection of a signal with the
modulation and spreading characteristics of an IEEE 802.15.4 compliant signal.
The signal strength may be above or below the ED threshold.
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8266C-MCU Wireless-08/11