Tx Fifo Packet Organization; Tx Buffers For Ack Payload; Structure Of Packets In The Tx Fifo; Segments For Holding Ack Payload For Each Address Entry - Texas Instruments CC253x User Manual

Packet Format

25.8.2 TX FIFO Packet Organization

Length
1 Byte
The structure of a packet in the TX FIFO is shown in
regardless of whether a length byte is present on the air. The length is the number of bytes in the address,
config, and payload fields following the length byte, and it may be modified before being transmitted on the
air. If a fixed length is used, it is up to the MCU to ensure that the length is correct given the fixed length
expected by the receiver. If packets are longer than what can fit in the FIFO, packets must be written to
the FIFO while transmission takes place, either by DMA or directly by the MCU. Auto-commit and auto-
deallocate must then be enabled for the TX FIFO in RFFCFG.
The address byte is placed after the length byte and is present if configured in
PRF_FIFO_CONF.TX_ADDR_CONF. If it is included, the address is transmitted on the air as it is read from
the FIFO. If it is not included, but a config byte is included, the three LSBs of the config byte tell the index
n of PRF_ADDR_ENTRYn from which the address is inserted. If neither an address nor a config byte is
included, the address is inserted from PRF_ADDR_ENTRY0.ADDRESS.
The config byte following the length byte and optional address byte is present if configured in
PRF_FIFO_CONF.TX_ADDR_CONF. This byte contains an address index which is used to determine the
address if no address byte is included as explained previously. If an address byte is included, the address
index is used to determine which address entry to read the configuration from, but the ADDRESS field in
that address entry is ignored. In auto mode, the NO_ACK bit (LSB) of the transmitted header is set to bit 5
of the config byte. If PRF_ADDR_ENTRYn.CONF.FIXEDSEQ, where n is the index of the address used, is
1, the SEQ field of the transmitted header is taken from the SEQ field (bits 6–7) of the config byte;
otherwise, the sequence number on the air is inserted from PRF_ADDR_ENTRYn.SEQSTAT.SEQ. If the
config byte is not included, the NO_ACK bit is always sent as 0 and
PRF_ADDR_ENTRYn.CONF.FIXEDSEQ should be 0 (otherwise the SEQ field always remains 0).The
payload is transmitted as present in the FIFO.

25.8.3 TX Buffers for ACK Payload

The hardware TX FIFO is not used for ACK payload in RX tasks in auto mode. Instead, an
acknowledgment packet for each address can be placed in one of two dedicated buffers for that address.
These two buffers constitute a FIFO capable of holding two packets. The buffers for the first two
addresses are placed in the RAM page normally used for the hardware TX FIFO. These four buffers can
either be accessed from the TX FIFO space at 0x6100 or by selecting page 7 through RFRAMCFG, but the
TX FIFO registers should not be used. The other twelve buffers must be addressed from the configurable
radio memory bank through the RFRAMCFG register. The mapping of each buffer is shown in
Table 25-11. Segments for Holding ACK Payload for Each Address Entry
Address Entry Number
0
0
1
1
2
300 CC2541 Proprietary Mode Radio
config
Address
0–1 Bytes 0–1 Bytes
Address Index Unused
LSB Bit 1 Bit 2 Bit 3
Figure 25-11. Structure of Packets in the TX FIFO
Buffer Number
0
1
0
1
0
Copyright © 2009–2014, Texas Instruments Incorporated
Payload
(Length – (Length of Address + config)) Bytes
NOA SEQ
Bit 4 Bit 5 Bit 6 MSB
Figure 25-11. All packets start with a length byte,
Setting of RFRAMCFG
7 or X
7 or X
7 or X
7 or X
1
SWRU191F – April 2009 – Revised April 2014
www.ti.com
R0014-02
Table 25-11.
Start Address
0x6000 or 0x6100
0x6020 or 0x6120
0x6040 or 0x6140
0x6060 or 0x6160
0x6000
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