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Link Layer Engine
Table 25-18. End-of-Receive Tasks (continued)
Condition End-of-Task Cause Comment
Did not get sync in the time specified by
TASK_NOSYNC
PRF_SEARCH_TIME
Received command for starting new task or If transmitter was running or receiver was
CMD_SHUTDOWN or observed Timer 2 event 2 with running and had obtained sync, an
TASK_ABORT
PRF_TASK_CONF.STOP_CONF = 10 RXTXABO interrupt is also raised.
LLEERR interrupt is also raised. If
transmitter was running or receiver was
Received unknown command TASKERR_CMD
running and had obtained sync, an
RXTXABO interrupt is also raised.
Task ends without any radio operation.
Semaphore is not free when expected TASKERR_SEM
LLEERR interrupt is also raised.
Unpermitted value of RAM register TASKERR_PAR
LLEERR interrupt is also raised.
For PRF_TASK_CONF.MODE = 00:
TASKERR_PAR
LLEERR interrupt is also raised.
PRF_ADDR_ENTRYn.RXLENGTH corresponding
to the received address is smaller than address length
For auto mode:
TASKERR_PAR
PRF_ADDR_ENTRYn.ACKLENGTGHm for the LLEERR interrupt is also raised.
ACK payload to be transmitted exceeded 32
25.9.2.4 Transmit Task
When a CMD_TX command is received, the LLE configures the radio on the channel given by
PRF_CHAN.FREQ and starts transmitting the packet from the Tx FIFO.
If the Tx FIFO has no available data, the task ends with TASKERR_TXFIFO as the end cause. Otherwise,
the number of bytes given by the length byte in the Tx FIFO is read from the Tx FIFO and transmitted or
otherwise handled as described in following sections. No check of data availability is done after the length
byte is read, so if the FIFO contains fewer bytes than indicated in the length field, a Tx FIFO underflow
interrupt is raised by the FIFO hardware.
25.9.2.4.1 Basic Mode
This section describes the transmit operation if PRF_TASK_CONF.MODE is 00 or 01.
If PRF_TASK_CONF.MODE is 01, the length field is calculated from the length field in the FIFO and
transmitted. It is up to the MCU to ensure that the calculated length field does not exceed 255. If
PRF_TASK_CONF.MODE is 00, no length field is transmitted.
If an address is configured, it is found based on the setting in PRF_FIFO_CONF.TX_ADDR_CONF. It can
be set to take the address from PRF_ADDR_ENTRY0, to read it from the Tx FIFO (which for the transmitter
is equivalent to not having an address configured), or to read an index n from the config byte in the FIFO
and read the address from PRF_ADDR_ENTRYn.ADDRESS. The values of ENA0 and ENA1 in
PRF_ADDR_ENTRYn.CONF are ignored for the transmitter; the primary sync word is always transmitted.
The payload (if any) is transmitted as given in the FIFO.
If configured, a CRC with the number of bytes given by PRF_CRC_LEN is transmitted at the end.
When a packet has been transmitted, the LLE sends a deallocate Tx FIFO command if
PRF_ADDR_ENTRYn.REUSE is 0. Otherwise, the MCU must issue either a deallocate Tx FIFO (to send a
new packet) or a retry Tx FIFO (to reuse) before sending again. The PRF_N_TX counter is incremented. A
TXDONE interrupt to the MCU is raised. The next action is as given in Section 25.9.2.3.3.
25.9.2.4.2 Auto Mode
This section describes the transmit operation if PRF_TASK_CONF.MODE is 10 or 11.
323
SWRU191C–April 2009–Revised January 2012 CC2541 Proprietary Mode Radio
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