Texas Instruments SimpleLink CC2620 Technical Reference Manual page 1596

Proprietary Radio
23.7.5.5.1 Common Carrier-Sense Description
The parameters for the carrier-sense operation are common for all the commands, and are given in . This
table gives the offset from the first byte used for carrier-sense parameters.
The channel can be in one of three states: BUSY, IDLE, or INVALID. BUSY indicates a signal on the
channel. IDLE indicates no signal is present on the channel. INVALID indicates that the state cannot be
determined. There are two sources of channel information, RSSI and correlation, and a separate state is
maintained for each source.
The operation starts when the radio has been set up in receive mode. The RSSI or correlation is
monitored, according to the enable bits csConf.bEnaRssi and csConf.bEnaCorr. If csConf.bEnaRssi is 1,
the RSSI is monitored. If csConf.bEnaCorr is 1, the correlator is set up to correlate against the preamble.
It is not possible to set both enable bits to 0.
If csConf.bEnaRssi is 1, the RSSI is monitored every time a new value is available from the radio. At each
update, the RSSI is compared against the signed value rssiThr. If the RSSI is below rssiThr and
numRssiIdle consecutive RSSI measurements below the threshold have been observed, the RSSI state is
IDLE. If the RSSI is above rssiThr and numRssiBusy consecutive RSSI measurements above the
threshold have been observed, the RSSI state is BUSY. Otherwise, the RSSI state is INVALID.
If csConf.bEnaCorr is 1, the radio CPU monitors correlation peaks from the modem. When the radio
starts, the state is INVALID. If no correlation top is observed until corrPeriod RAT ticks after the carrier
sense command was started, the state becomes IDLE. If the state is IDLE and at least
corrConfig.numCorrInv correlation tops with at most corrPeriod RAT ticks between them are observed, the
state becomes Invalid. If the state is INVALID and at least corrConfig.numCorrBusy correlation tops with
at most corrPeriod RAT ticks between them are observed, the state becomes BUSY. If
corrConfig.numCorrBusy is 0, the state goes directly to BUSY from IDLE. The value of
corrConfig.numCorrIdle must be greater than 0. If the state is not Idle and corrTime RAT ticks pass after
the last correlation top, the state becomes IDLE again.
If only one of the enable bits is 1, the channel state is equal to the state of the corresponding source. If
both enable bits are 1, the channel state depends on the state of the two sources and the
csConf.operation bit, as shown in
csConf.operation = 0
Correlation state
RSSI State
Invalid
Invalid Invalid
Idle Invalid
Busy Busy
csConf.operation = 1
Correlation state
RSSI State
Invalid
Invalid Invalid
Idle Idle
Busy Invalid
If the state of the channel changes to BUSY, the action depends on csConf.busyOp and the command
being run. If csConf.busyOp is 0, the operation continues. If csConf.busyOp is 1 and the command is
CMD_PROP_CS, the operation ends with PROP_DONE_BUSY as status.
If the state of the channel changes to IDLE, the action depends on csConf.idleOp. If the value of this field
is 0, the receiver and carrier sense operation continues. If it is 1, the operation ends with
PROP_DONE_IDLE as status.
If the trigger given by csEndTrigger and csEndTime is observed, the action depends on the command
being run and the channel state at that time. The details are described in
1596
Radio
Table 23-152.
Table 23-152. Channel State When Both Sources are Enabled
Copyright © 2015, Texas Instruments Incorporated
Idle
Invalid
Idle
Busy
Idle
Idle
Idle
Idle
SWCU117C – February 2015 – Revised September 2015
www.ti.com
Busy
Busy
Busy
Busy
Busy
Invalid
Idle
Busy
Section 23.7.5.5.2 and .
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