SWCU192 November 2021 CC1312R7 , CC1352P7 , CC2652P7 , CC2652R7
26.10.4.1 Receive Buffers
A packet being received is stored in a receive buffer. First, a length byte or word is stored if configured in the RX entry by config.lenSz, and calculated from the length received over the air and the configuration of appended information, or for a partial-read RX buffer initialized to maximal possible size of that segment, and set to the length of the segment in one buffer when finished.
Following the optional length field, the received header is stored as received over the air if rxConf.bIncludeHdr is 1. This header is the length byte for CMD_PROP_RX and a field with up to 32 bits for CMD_PROP_RX_ADV. In the latter case, the last byte of the header is padded with zeros in the MSBs if the number of bits does not divide by 8, and followed by the received address (if configured) and payload.
If rxConf.bIncludeCrc is 1, the received CRC value is stored in the RX buffer; otherwise, it is not stored, but only used to check the CRC result. If rxConf.bAppendRssi is 1, a byte indicating the received RSSI value is appended. If rxConf.bAppendStatus is 1, a status byte of the type defined in Table 26-180 is appended. If rxConf.bAppendTimeStamp is 1, a timestamp indicating the start of the packet is appended. This timestamp corresponds to the ratmr_t data type. Though the timestamp is multibyte, no word-address alignment is made, so the timestamp must be written and read bytewise.
If the reception of a packet is aborted, the packet is immediately removed from the receive queue, except if a partial-read RX entry is used. In that case, the RSSI, Timestamp, and Status fields are appended if configured (except if no more buffer space is available), and the Status byte indicates that the reception was aborted.
Figure 26-11 shows the format of an entry element in the RX queue.
Figure 26-11 Receive Buffer Entry ElementAn RX_ENTRY_DONE interrupt is raised when an RX entry changes its state to Finished. Depending on the type of RX entry used, this means:
- For a general or pointer entry, an RX_ENTRY_DONE interrupt is raised after a packet is fully received, unless the packet is automatically flushed.
- For a multielement entry, an RX_ENTRY_DONE interrupt is raised when a new buffer is allocated and a new entry was taken into use, or when a buffer is finished and fills the entire entry.
- For a partial-read entry, an RX_ENTRY_DONE interrupt is raised when an RX entry is full, so writing must continue in the next entry.
For partial-read entries, an RX_Data_Written interrupt is raised whenever data is written to the receive buffer. An RX_N_Data_Written is raised whenever a multiple of config.irqIntv (as given in the data entry) bytes have been written since the start of the packet.