AN633
Rev. 0.7
63
PSDU (p CRC). The PHR contains fields to select between 2– and 4–byte CRCs (FCS field), data
whitening enable/disable (DW field), and length (Length field). The mode switching field (MS field) is disabled (not
supported by the radio). The packet feature and the naming convention of the standard and the radio IC are shown
in Figure 45.
Figure 45. Packet Structure and Naming Convention (802.15.4g–blue, Si4468–orange)
The Si446x supports automatic PHR parsing (see GLOBAL_CONFIG:PROTOCOL in the API) which makes it
possible to receive packets sent in different ways. Once configured correctly and in receive mode, the radio may
receive any packet regardless of how it was sent: with 2– or 4–byte CRC, with or without data whitening, and
without initially knowing how many bytes to expect. It recognizes the FCS, DW, and Length fields of the PHR, and
based on that information, it runs the built-in, 16– or 32–bit built-in CRC engine, enables or disables data
whitening, and receives the right amount of bytes. A given packet can be sent in one of four ways:
16-bit CRC, DW disabled
16-bit CRC, DW enabled
32-bit CRC, DW disabled
32-bit CRC, DW enabled
No matter which of these four options is used to send a packet in the example project, the RX side will receive the
packet, and send back the ACK accordingly. That is to say if a project is configured to send a packet with 16-bit
CRC, DW disabled, it is still able to receive a packet with 32-bit CRC, DW enabled and blinks the LED as long as
the payload content is correct. The PHR can be different, but the payload has to be the same. The ACK that it
sends back will match that of the sender, 32-bit CRC, DW enabled.
To support the two FCSs, CRC-16 and CRC-32, there are two built-in CRC engines in the radio IC that are running
in parallel (referred to as Primary and Alternative CRC in the code). The Alternative is used for 32-bit, the Primary
for the 16-bit CRC. The PHR parser will pick the right one to calculate the CRC.
On the transmit side there is no automatic parsing. The PHR field has to be entered manually into the TX FIFO,
and the user application has to select the right CRC, enable/disable data whitening accordingly. Note that the CRC
and data whitening apply only to the PSDU payload which excludes the PHR. Due to this, two fields are configured:
Field 1 for the PHR with no CRC and DW, and Field 2 for the p CRC with optional DW.
MAC
header
MAC
payload
MAC
footer
(MHR)
(MFR)
PPDU
(PHY
Protocol
Data
Unit)
SHR
PHR
PSDU
(Synchronization
header)
(PHY
header)
(PHY
Service
Data
Unit
or
PHY
payload)
SHR
SHR
Bit
0
1
‐
2
3
4
5
‐
15
Preamble
Sync
field
MS
R1
‐
R0
FCS
type
DW
L10
‐
L0
Payload
FCS
Preamble
Sync
word
Field
1
Field
2
Содержание EZRADIOPRO Si4060
Страница 24: ...AN633 24 Rev 0 7 Figure 20 Supply Current versus Time Diagram from Shutdown to RX State...
Страница 67: ...AN633 Rev 0 7 67 Figure 48 Variable Length Packet Reception Flowchart...
Страница 69: ...AN633 Rev 0 7 69 Figure 50 Packet Matching Reception Flowchart...
Страница 73: ...AN633 Rev 0 7 73 Figure 54 Packet Reception with Automatic RX Hopping Flowchart...
Страница 75: ...AN633 Rev 0 7 75 Figure 56 Packet Reception with Manual Rx Hopping...
Страница 80: ...AN633 80 Rev 0 7 Figure 62 Long Packet Transmission Workflow...
Страница 81: ...AN633 Rev 0 7 81 Figure 63 Long Packet RX Flowchart...