Data Sheet

CC1101
SWRS061B Page 72 of 93
0x16: MCSM2 – Main Radio Control State Machine Configuration
Bit Field Name Reset R/W Description
7:5 Reserved R0 Reserved
4 RX_TIME_RSSI 0 R/W Direct RX termination based on RSSI measurement (carrier sense). For
ASK/OOK modulation, RX times out if there is no carrier sense in the first 8
symbol periods.
3 RX_TIME_QUAL 0 R/W
When the RX_TIME timer expires, the chip checks if sync word is found
when RX_TIME_QUAL=0, or either sync word is found or PQI is set when
RX_TIME_QUAL=1.
RX_TIME[2:0] 7 (111) R/W Timeout for sync word search in RX for both WOR mode and normal RX
operation. The timeout is relative to the programmed EVENT0 timeout.
2:0
The RX timeout in µs is given by EVENT0·C(RX_TIME, WOR_RES) ·26/X, where C is given by the table below and X is
the crystal oscillator frequency in MHz:
Setting WOR_RES = 0 WOR_RES = 1 WOR_RES = 2 WOR_RES = 3
0 (000) 3.6058 18.0288 32.4519 46.8750
1 (001) 1.8029 9.0144 16.2260 23.4375
2 (010) 0.9014 4.5072 8.1130 11.7188
3 (011) 0.4507 2.2536 4.0565 5.8594
4 (100) 0.2254 1.1268 2.0282 2.9297
5 (101) 0.1127 0.5634 1.0141 1.4648
6 (110) 0.0563 0.2817 0.5071 0.7324
7 (111) Until end of packet
As an example, EVENT0=34666, WOR_RES=0 and RX_TIME=6 corresponds to 1.96 ms RX timeout, 1 s polling interval
and 0.195% duty cycle. Note that WOR_RES should be 0 or 1 when using WOR because using WOR_RES > 1 will give a
very low duty cycle. In applications where WOR is not used all settings of WOR_RES can be used.
The duty cycle using WOR is approximated by:
Setting
WOR_RES=0 WOR_RES=1
0 (000) 12.50% 1.95%
1 (001) 6.250% 9765ppm
2 (010) 3.125% 4883ppm
3 (011) 1.563% 2441ppm
4 (100) 0.781% NA
5 (101) 0.391% NA
6 (110) 0.195% NA
7 (111) NA
Note that the RC oscillator must be enabled in order to use setting 0-6, because the timeout counts RC oscillator
periods. WOR mode does not need to be enabled.
The timeout counter resolution is limited: With RX_TIME=0, the timeout count is given by the 13 MSBs of EVENT0,
decreasing to the 7MSBs of EVENT0 with RX_TIME=6.