Zigbee MAC layer frames
As mentioned in the zigbee protocol stack that zigbee MAC layer frame composed of MAC header,MAC payload and FCS. The diagram below depicts generic mac frame format adopted in zigbee technology at MAC layer. This part is also referred as MPDU or MAC Protocol Data Unit. This gets embedded into PPDU(physical PDU) frame of zigbee.
Generic MAC Frame format
| Octets:2 | 1 | 0/2 | 0/2/8 | 0/2 | 0/2/8 | Var | 2 |
|---|---|---|---|---|---|---|---|
| Frame control | Sequence number | Destination PAN ID | Destination Address | Source PAN ID | Source Address | Frame Payload | FCS |
| Addressing fields | |||||||
| MHR | MAC Payload | MFR | |||||
Generic MAC layer frame has frame control field of 2 octets. It carries useful information such as frame type, source and destination addressing modes. Frame type specifies whether the frame is beacon frame,data frame, ACK of data, MAC command frame etc. The same is outlined 'Frame type subfield' table below with 3 bits.
Frame control field
| Bits: 0-2 |
3 | 4 | 5 | 6 | 7-9 | 10-11 | 12-13 | 14- 15 |
|---|---|---|---|---|---|---|---|---|
| Frame type |
security enabled |
Frame pending |
Ack. Request |
Intra PAN |
Reserved | Dest. Addre- ssing mode |
Reserved | Source Addre- ssing mode |
Frame type subfield
| Frame type value (b2,b2,b0) |
Description |
|---|---|
| 000 | Beacon frame |
| 001 | Data frame |
| 010 | Acknowledgement |
| 011 | MAC command |
| 100-111 | Reserved |
As shown below beacon frame carries frame control field and addressing fields along with sequence number. It is broadcasted to obtain PAN ID of nearby zigbee devices.
Beacon Frame format
| Octets:2 | 1 | 4/10 | 2 | var | var | var | 2 |
|---|---|---|---|---|---|---|---|
| Frame control |
sequence number |
Addressing fields |
Superframe specification |
GTS fields | Pending address fields |
Beacon payload |
FCS |
| MHR | MAC Payload | MFR | |||||
Once connection is established data frame carry data. The format of data frame is similar to generic mac frame format and is shown in the table below.
Data Frame format
| Octets:2 | 1 | section 7.2.2.2.1 IEEE 802.15.4 |
Variable | 2 |
|---|---|---|---|---|
| Frame control |
sequence number |
Addressing fields |
Data Payload |
FCS |
| MHR | MAC Payload | MFR | ||
Acknowledgement Frame format
| Octets:2 | 1 | 2 |
|---|---|---|
| Frame control | sequence number | FCS |
| MHR | MFR | |
MAC command Frame format
| Octets:2 | 1 | section 7.2.2.4.1 IEEE 802.15.4 | 1 | Variable | 2 |
|---|---|---|---|---|---|
| Frame control | sequence number | Addressing fields | Command Frame Identifier | Command Payload | FCS |
| MHR | MAC Payload | MFR | |||
Zigbee protocol supports different command frames for difference use case as mentioned below in the table.
MAC command frames
| Command Frame ID | Command frame |
|---|---|
| 0x01 | Association request(Tx) |
| 0x02 | Association response(Rx) |
| 0x03 | Disassociation notification(Tx,Rx) |
| 0x04 | Data request(Tx) |
| 0x05 | PAN ID conflict notification(Tx) |
| 0x06 | Orphan notification(Tx) |
| 0x07 | Beacon request(Tx) |
| 0x08 | coordinator realignment(Rx) |
| 0x09 | GTS Request |
| 0x0a-0xFF | Reserved |
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