Texas Instruments CC2541 User Manual

Bytes:
0 to 20
Frame Payload
n
2
MAC Header (MHR) MAC Payload
Bytes:
1 1
5 + (0 to 20) + n4
11 + (0 to 20) + n
MAC
Layer
PHY
Layer
M0108-01
2 1
Frame
ControlField
(FCF)
Data
Sequence
Number
Address
Information
FrameCheck
Sequence
(FCS)
MAC Footer
(MFR)
MACProtocol
Data Unit
(MPDU)
PHY ServiceDataUnit
(PSDU)
Preamble
Sequence
Start-of-Frame
Delimiter
(SFD)
Frame
Length
SynchronizationHeader
(SHR)
PHY Header
(PHR)
PHY Protocol DataUnit
(PPDU)
IEEE 802.15.4-2006 Frame Format www.ti.com
23.7 IEEE 802.15.4-2006 Frame Format
This section gives a brief summary of the IEEE 802.15.4 frame format [1]. The radio has built-in support
for processing of parts of the frame. This is described in the following sections.
Figure 23-3 shows a schematic view of the IEEE 802.15.4 frame format. Similar figures describing specific
frame formats (data frames, beacon frames, acknowledgment frames, and MAC command frames) are
included in the standard document [1].
Figure 23-3. Schematic View of the IEEE 802.15.4 Frame Format [1]
23.7.1 PHY Layer
Synchronization Header
The synchronization header (SHR) consists of the preamble sequence followed by the start-of-frame
delimiter (SFD). In the IEEE 802.15.4 specification [1], the preamble sequence is defined to be 4 bytes of
0x00. The SFD is one byte with value 0xA7.
PHY Header
The PHY header consists only of the frame-length field. The frame-length field defines the number of
bytes in the MPDU. Note that the value of the frame-length field does not include the frame-length field
itself. It does, however, include the frame-check sequence (FCS), even if this is inserted automatically by
the hardware.
The frame-length field is 7 bits long and has a maximum value of 127. The most-significant bit in the
frame-length field is reserved, and should always be set to zero.
PHY Service Data Unit
The PHY service data unit (PSDU) contains the MAC protocol data unit (MPDU). It is the MAC layer's
function to generate/interpret the MPDU, and the radio has built-in support for processing of some of the
MPDU subfields.
23.7.2 MAC Layer
The FCF, data sequence number, and address information follow the frame-length field as shown in
Figure 23-3. Together with the MAC data payload and frame check sequence, they form the MPDU. The
format of the FCF is shown in Figure 23-4. For full details, see the IEEE 802.15.4 specification [1].
Bits: 0–2 3 4 5 6 7–9 10–11 12–13 14–15
Frame type Security Frame Acknowledge Intra PAN Reserved Destination Reserved Source
enabled pending request addressing addressing
mode mode
Figure 23-4. Format of the Frame Control Field (FCF)
228
CC253x Radio SWRU191C–April 2009–Revised January 2012
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Texas Instruments CC2541 Specifications

General

Brand	Texas Instruments
Model	CC2541
Category	Microcontrollers
Language	English