EM2420 ETC [List of Unclassifed Manufacturers], EM2420 Datasheet - Page 37

• Manufacturer Part Number: EM2420
• Description: 2.4 GHz IEEE 802.15.4 / ZigBee RF Transceiver
• Manufacturer: ETC [List of Unclassifed Manufacturers]

Link Quality Indication section on page 49
for details.
Figure 18. The EM2420 Frame Check Sequence (FCS) hardware implementation [1]
Figure
RF Data Buffering
The EM2420 can be configured for different
transmit and receive modes, as set in the
MDMCTRL1.TX_MODE
MDMCTRL1.RX_MODE
Buffered mode (mode 0) will be used for
normal operation of the EM2420, while
other
purposes.
Buffered transmit mode
In buffered transmit mode (TX_MODE 0),
the 128 byte TXFIFO, located in the
EM2420 RAM, is used to buffer data before
transmission.
(defined in the Frame Format section
below) is automatically inserted before the
length field during transmission. The
length field must always be the first byte
written to the transmit buffer for all frames.
Writing one or multiple bytes to the
TXFIFO is described in the FIFO access
section on page 29. Reading data from the
TXFIFO is possible with RAM access, but
Ember Part Number: 120-0049-000C
(LSB
Data
input
first)
Data in RXFIFO
modes
r0
19.
r1
A
Length byte
are
Data
r2
preamble
n
available
r3
control
in
MPDU
r4
sequence
for
1
RXFIFO
r5
bits.
and
test
EM2420 Datasheet
MPDU
r6
2
r7
when
Bit number
The most significant bit in the last byte of
each frame is set high if the CRC of the
received
otherwise.
this does not remove the byte from the
FIFO.
Transmission is enabled by issuing a
STXON or STXONCCA command strobe.
See the Radio control state machine
section on page 42 for an illustration of
how the transmit command strobes affect
the state of the EM2420. The STXONCCA
strobe is ignored if the channel is busy.
See
r8
r9
MDMCTRL0.AUTOCRC
MPDU
r10
CRC
OK
frame
7
MPDU
6
r11
Correlation value (unsigned)
is
n-2
5
r12
correct
EM2420
4
(signed)
r13
RSSI
3
r14
Page 37 of 89
and
is
2
CRC / Corr
r15
1
low
set
the
0