EM2420-STR Ember, EM2420-STR Datasheet - Page 31

• 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: -

Transmit mode
During transmit, the FIFO and FIFOP pins
are still only related to the RXFIFO.
However, the SFD pin is active during
transmission of a data frame, as shown in
Figure 13.
The SFD pin goes high when the SFD field
has been completely transmitted. It goes
low again when the complete MPDU (as
defined by the length field) has been
transmitted or if an underflow is detected.
General control and status pins
In receive mode, the FIFOP pin can be
used to interrupt the microcontroller when
a threshold has been exceeded or a
complete frame has been received. This
pin should then be connected to a
microcontroller interrupt pin.
In receive mode, the FIFO pin can be
used to detect if there is data at all in the
receive FIFO.
The SFD pin can be used to extract the
timing information of transmitted and
Demodulator, Symbol Synchronizer and Data Decision
The
demodulator is shown in Figure 14.
Channel filtering and frequency offset
compensation is performed digitally. The
signal level in the channel is estimated to
generate the RSSI level (see the RSSI /
Energy Detection section on page 45 for
more information). Data filtering is also
included for enhanced performance.
With the ±40 ppm frequency accuracy
requirement from [1], a compliant receiver
must be able to compensate for up to 80
Ember Part Number: 120-0049-000D
Data transmitted
SFD Pin
over RF
block
12 symbol periods
diagram
Figure 13. Pin activity example during transmit
for
Automatically generated
preamble and SFD
Preamble
the
EM2420
SFD Length
EM2420 Datasheet
See the RF Data Buffering section on
page 35 for more information on TXFIFO
underflow.
As can be seen from comparing Figure 11
and Figure 13, the SFD pin behaves very
similarly during reception and transmission
of a data frame. If the SFD pins of the
transmitter and the receiver are compared
during the transmission of a data frame, a
small delay of approximately 2 µs can be
seen because of bandwidth limitations in
both the transmitter and the receiver.
received data frames. The SFD pin will go
high when a start of frame delimiter has
been completely detected / transmitted.
The
connected to a timer capture pin on the
microcontroller.
For debug purposes, the SFD and CCA
pins can be used to monitor several status
signals as selected by the IOCFG1
register. See Table 12 and Table 13 for
available signals.
The polarity of FIFO, FIFOP, SFD and CCA
can be controlled by the IOCFG0 register
(address 0x1C).
ppm or 200 kHz. The
tolerates up to 300 kHz offset without
significant degradation of the receiver
performance.
Soft decision is used at the chip level, i.e.,
the demodulator does not make a decision
for each chip, only for each received
symbol. De-spreading is performed using
over sampled symbol correlators. Symbol
synchronization
continuous start of frame delimiter (SFD)
search.
SFD
Data fetched
from TXFIFO
MAC Protocol Data Unit (MPDU)
pin
should
is
EM2420
achieved
EM2420
preferably
demodulator
CRC generated
Page 31 of 84
by
CC2420
by
be
a