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Link Layer Engine
Table 25-13. Timer 2 Capture Settings (continued)
00 Capture of received packets off
01 Capture the start (after the sync word) of every received packet
10 Capture the end of every received packet
Capture the start of the first received packet, i.e., capture of received packets is turned off after
11
a packet has been fully received.
When capture is done at the beginning of a packet, the time captured is the time right after the sync word
has been received or transmitted. Setting TXCAP or RXCAP to 11 enables capture at the start of a packet,
but the capture is turned off after a packet has been transmitted or fully received in a task, so it is the start
of the first packet in the task that is captured. The MCU should normally only read the captured value after
a task is done; otherwise, the captured value may be overwritten with a new value. The user must take
into account that a timer value may be captured on a received packet that does not match the address or
that has a length which is not permitted, and that is thus not reported. It is possible to turn on capture for
both received and transmitted packets in the same task. If so, it is up to the user to determine if the
captured value was from a received or transmitted packet.
When a task is finished, the LLE writes an end-of-task cause in PRF_ENDCAUSE, frees the semaphores,
raises a TASKDONE interrupt, and halts its operation. The possible values of PRF_ENDCAUSE are listed in
Table 25-14.
If PRF_CHAN.SYNTH_ON is 1, the synthesizer is not turned off after the task ends. This can be used to
start a new task immediately on the same channel and get faster start of Rx or Tx. To do so, the next task
should be started with PRF_CHAN.FREQ set to 127. Note that the synthesizer should not be allowed to run
for a long time after a task has ended, as this causes excessive power consumption. The synthesizer can
be stopped by sending a CMD_SHUTDOWN command.
Table 25-14. End-of-Task Causes
Number Name Description
Normal task ending
0 TASK_ENDOK Task ended normally
Timer 2 event 2 or CMD_STOP observed while waiting for Rx
1 TASK_RXTIMEOUT
sync
2 TASK_NOSYNC Sync was not obtained in the specified time
3 TASK_NOCC TX_ON_CC ended because channel was not clear
Task ended because maximum number of retransmissions was
4 TASK_MAXRT
reached
Task ended after transmission or reception by Timer 2 event 2
5 TASK_STOP or CMD_STOP while transmitting or receiving or with ACK or
retransmission in progress
6 TASK_ABORT Task aborted by command
MCU interface error
255 TASKERR_INTERNAL Internal program error
254 TASKERR_CMD Unknown command
253 TASKERR_SEM Unable to obtain semaphore
252 TASKERR_PAR Unpermitted parameter
251 TASKERR_TXFIFO Tx FIFO without available data when not permitted
250 TASKERR_RXFIFO Overfull Rx FIFO in Tx task
249 TASKERR_MODUNF Modulator underflow observed
317
SWRU191C–April 2009–Revised January 2012 CC2541 Proprietary Mode Radio
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