CC2420 Chipcon AS, CC2420 Datasheet - Page 33

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

Length field
The frame length field shown in Figure 15
defines the number of bytes in the MPDU.
Note that the length field does not include
the length field itself. It does however
include
Sequence),
automatically by
includes the MIC if authentication is used.
The length field is 7 bits and has a
maximum
significant bit in the length field is reserved
[1], and should be set to zero.
CC2420
both for transmission and reception, so
this field must always be included even if
implementing a proprietary (non 802.15-4)
system.
Bits: 0-2
Frame
Type
Frame check sequence
A 2-byte frame check sequence (FCS)
follows the last MAC payload byte as
shown in Figure 15. The FCS is calculated
over the MPDU, i.e. the length field is not
part of the FCS. This field is automatically
generated and verified by hardware when
Chipcon AS SmartRF ® CC2420 Preliminary Datasheet (rev 1.0), 2003-11-17
IEEE 802.15.4
hardware uses the length field
3
Security
Enabled
the
CC2420
value
even
CC2420
FCS
Figure 17. Format of the Frame Control Field (FCF) [1]
4
Frame
Pending
of
if
Figure 16. Transmitted Synchronisation Header
2·(PREAMBLE_LENGTH + 1) zero symbols
0
127.
this
(Frame
hardware. It also
0
5
Acknowledge
request
is
The
inserted
Check
0
most
SW0 = SYNCWORD[3:0]
SW1 = SYNCWORD[7:4]
SW2 = SYNCWORD[11:8]
SW3 = SYNCWORD[15:12]
Preamble
0
6
Intra
PAN
Synchronisation Header
SmartRF
0
In transmit mode, the length field is used
for underflow detection, as described in
the FIFO access section on page 27.
MAC protocol data unit
The FCF, data sequence number and
address information follows the length field
as shown in Figure 15. Together with the
MAC data payload and Frame Check
Sequence, they form the MAC Protocol
Data Unit (MPDU).
The format of the FCF is shown in Figure
17. Please refer to [1] for details.
There is no hardware support for the data
sequence number, this field must be
inserted and verified by software.
CC2420
recognition, as described in the Address
Recognition section on page 36.
the MODEMCTRL0.AUTOCRC control bit is
set. It is recommended to always have this
enabled,
purposes. If cleared, CRC generation and
verification
software.
7-9
Reserved
0
if different from 'F', else '0'
if different from 'F', else '0'
if different from 'F', else '0'
if different from 'F', else '0'
SW0
includes
except
0
10-11
Destination
addressing
mode
must
SW1
0
®
possibly
be
hardware
SW2
12-13
Reserved
CC2420
7
SFD
performed
SW3
A
for
Page 33 of 85
14-15
Source
addressing
mode
address
debug
by