Ieee 802.15.4-2006 Frame Format; Phy Layer; Mac Layer; Schematic View Of The Ieee 802.15.4 Frame Format - Texas Instruments CC253x User Manual

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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].
MAC
Layer
Bytes: 4
Start-of-Frame
PHY Preamble
Delimiter
Layer Sequence
Synchronization Header
(SHR)
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). The functino of the MAC
layer is to generate or 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
Bits: 0–2 3
Frame type Security
enabled
SWRU191F – April 2009 – Revised April 2014
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Bytes: 2
Frame
Control Field
(FCF)
1 1
Frame
Length
(SFD)
PHY Header
(PHR)
Figure 23-4. For full details, see the IEEE 802.15.4 specification [1].
4 5
Frame Acknowledge
pending request
Figure 23-4. Format of the Frame Control Field (FCF)
Copyright © 2009–2014, Texas Instruments Incorporated
1 0 to 20
Data
Address
Sequence
Information
Number
MAC Header (MHR)
5 + (0 to 20) + n
MAC Protocol
Data Unit
(MPDU)
PHY Service Data Unit
(PSDU)
11 + (0 to 20) + n
PHY Protocol Data Unit
(PPDU)
6 7–9
Intra PAN Reserved Destination
IEEE 802.15.4-2006 Frame Format
n
Frame Payload
MAC Payload
10–11 12–13
Reserved
addressing
mode
CC253x Radio
2
Frame Check
Sequence
(FCS)
MAC Footer
(MFR)
M0108-01
14–15
Source
addressing
mode
217