EM2420-STR Ember, EM2420-STR Datasheet - Page 47

• Manufacturer Part Number: EM2420-STR
• Description: IC RF TXRX ZIGBEE 2.4GHZ 48-QLP
• Manufacturer: Ember

Specifications of EM2420-STR

• Mfg Application Notes: EM2420
• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: 802.15.4
• Applications: ZigBee™
• Power - Output: -3dBm
• Sensitivity: -94dBm
• Voltage - Supply: 2.1 V ~ 3.6 V
• Current - Receiving: 19.7mA
• Current - Transmitting: 17.4mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 48-QLP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Memory Size: -

Clear Channel Assessment
The clear channel assessment signal is
based on the measured RSSI value and a
programmable
channel assessment function is used to
implement the CSMA-CA functionality
specified in [1]. CCA is valid when the
receiver has been enabled for at least 8
symbol periods.
Carrier
programmed by RSSI.CCA_THR. The
threshold value can be programmed in
steps of 1 dB. A CCA hysteresis can also
be
MDMCTRL0.CCA_HYST control bits.
All 3 CCA modes specified by [1] are
implemented in the
in MDMCTRL0.CCA_MODE, as can be seen
in the register description. The different
modes are:
Frequency and Channel Programming
The
programming the 10 bit frequency word
located
operating frequency F
F
In receive mode the actual LO frequency
is F
Direct conversion is used for transmission,
so here the LO frequency equals F
2 MHz IF is automatically set by the
EM2420
equal for RX and TX.
Ember Part Number: 120-0049-000D
C
= 2048 + FSCTRL.FREQ[9:0] MHz
C
– 2 MHz, since a 2 MHz IF is used.
operating
, so the frequency programming is
in
programmed
sense
FSCTRL.FREQ[9:0].
threshold.
frequency
threshold
EM2420
C
in MHz is given by:
. They are set
in
The
is
level
set
C
. The
clear
The
EM2420 Datasheet
the
by
is
0
1
2
3
Clear channel assessment is available on
the CCA output pin. CCA is active high, but
the polarity may be changed by setting the
IOCFG0.CCA_POLARITY control bit.
Implementing CSMA-CA may be done
most easily by using the STXONCCA
command strobe, as described in the
Radio control state machine section on
page 40. Transmission will then only start
if the channel is clear. The TX_ACTIVE
status bit (see Table 5) may be used to
detect the result of the CCA.
IEEE 802.15.4 specifies 16 channels
within the 2.4 GHz band, numbered 11
through 26. The RF frequency of channel
k is given by [1] :
F
For
FSCTRL.FREQ register should therefore
be set to:
FSCTRL.FREQ = 357 + 5 (k-11)
C
= 2405 + 5 (k-11) MHz, k=11, 12, ..., 26
Reserved
Clear channel when received energy is below
threshold.
Clear channel when not receiving valid IEEE
802.15.4 data.
Clear channel when energy is below threshold
and not receiving valid IEEE 802.15.4 data
operation
in
channel
EM2420
Page 47 of 84
k,
the