CC2420 Chipcon AS, CC2420 Datasheet - Page 32

• Manufacturer Part Number: CC2420
• Description: 2.4 GHz RF Transceiver for IEEE 802.15.4 and ZigBee
• Manufacturer: Chipcon AS

Figure 15 [1] shows a schematic view of
the IEEE 802.15.4 frame format. Similar
figures describing specific frame formats
Synchronisation header
The
consists
followed by the start of frame delimiter
(SFD). In [1], the preamble sequence is
defined to be 4 bytes of 0x00. The SFD is
one byte, set to 0xA7.
In
configurable. The default values are
compliant with [1]. Changing these values
will
compliant, which could be desirable in
some cases.
A
transmitted first in all transmit modes.
The preamble sequence length can be set
by MDMCTRL0.PREAMBLE_LENGTH, while
the SFD is programmed in the SYNCWORD
register. SYNCWORD is 2 bytes long, which
gives the user some extra flexibility as
described below. Figure 16 shows how the
CC2420
the IEEE 802.15.4 specification.
The programmable preamble length only
applies to transmission, it does not affect
Chipcon AS SmartRF ® CC2420 Preliminary Datasheet (rev 1.0), 2003-11-17
Layer
Layer
MAC
PHY
CC2420
synchronisation
Bytes:
make
synchronisation
synchronisation header relates to
, the preamble length and SFD is
Sequence
Preamble
Synchronisation Header
of
4
Figure 15. Schematic view of the IEEE 802.15.4 Frame Format [1]
the
the
(SHR)
system
Start of Frame
preamble
header
Delimiter
(SFD)
1
header
non-802.15.4-
PHY Header
Length
is
Frame
(PHR)
sequence
1
always
(SHR)
Bytes:
Control Field
Frame
(FCF)
2
PHY Protocol Data Unit
11 + (4 to 20) + n
MAC Header (MHR)
SmartRF
(PPDU)
Sequence
Number
(data
acknowledgment
command frames) are included in [1].
receive
should not be set shorter than the default
value. Note that 2 of the 8 zero-symbols in
the preamble sequence required by [1] are
included in the SYNCWORD register so that
the
symbols long for compliance with [1]. Two
additional zero symbols in SYNCWORD
make
In reception,
received zero-symbols and searches for
the
SYNCWORD register. The least significant
symbols in SYNCWORD set to 0xF will be
ignored, while symbols different from 0xF
will be required for synchronisation. The
default setting of 0xA70F thereby requires
one
synchronisation. This will reduce the
number of false frames detected due to
noise.
In receive mode
preamble
synchronisation
adjustments. The SFD is used for byte
synchronisation, and is not part of the data
stored in the receive buffer (RXFIFO).
Data
1
CC2420
SFD
CC2420
Information
additional
Address
0 to 20
PHY Service Data Unit
mode.
frames,
5 + (0 to 20) + n
preamble sequence is only 6
MAC Protocol
sequence
Data Unit
compliant with [1].
sequence
(MPDU)
(PSDU)
CC2420
and
The
®
frames
CC2420
Frame payload
MAC Payload
beacon
zero-symbol
CC2420
preamble
frequency
defined
synchronises to
n
for
and
Page 32 of 85
uses the
by
frames,
symbol
Frame Check
length
MAC Footer
offset
Sequence
MAC
(MFR)
(FCS)
the
2
for