CC2430 Datasheet, PDF (181/234 Pages) Texas Instruments – A True System-on-Chip solution for 2.4 GHz IEEE 802.15.4 / ZigBee-TM

CC2430
14.21 MAC Security Operations (Encryption and Authentication)
CC2430 features hardware IEEE 802.15.4
MAC security operations. Refer to section
14.22 Linear IF and AGC Settings
13.9 on page 135 for a description of the
AES encryption unit.
dynamic range by using an analog/digital
feedback loop.
C2430 is based on a linear IF chain where
the signal amplification is done in an
analog VGA (variable gain amplifier). The
gain of the VGA is digitally controlled.
The AGC characteristics are set through
the AGCCTRLL:AGCCTRLH, registers. The
reset values should be used for all AGC
control registers.
The AGC (Automatic Gain Control) loop
ensures that the ADC operates inside its
14.23 RSSI / Energy Detection
CC2430 has a built-in RSSI (Received
Signal Strength Indicator) giving a digital
value that can be read form the 8 bit,
signed 2’s complement RSSIL.RSSI_VAL
register bits.
The RSSI value is always averaged over 8
symbol periods (128 µs), in accordance
with [1].
The RSSI register value RSSI.RSSI_VAL
can be referred to the power P at the RF
pins by using the following equations:
P = RSSI_VAL + RSSI_OFFSET [dBm]
where the RSSI_OFFSET is found
empirically during system development
from the front end gain. RSSI_OFFSET is
approximately –45. E.g. if reading a value
of –20 from the RSSI register, the RF
input power is approximately –65 dBm.
A typical plot of the RSSI_VAL reading as
function of input power is shown in Figure
53. It can be seen from the figure that the
RSSI reading from CC2430 is very linear
and has a dynamic range of about 100 dB.
-100
-80
-60
-40
RF Level [dBm]
60
40
20
0
-20
0
-20
-40
-60
Figure 53: Typical RSSI value vs. input power
CC2430 PRELIMINARY Data Sheet (rev. 1.03) SWRS036A
Page 181 of 232