Texas Instruments 3138 155 232931 - Manual (Page 65)

CC2420
SWRS041B Page 65 of 89
MDMCTRL1 (0x12)– Modem Control Register 1
Bit Field Name Reset R/W Description
15:11 - 0 W0 Reserved, write as 0.
10:6 CORR_THR[4:0] 20 R/W Demodulator correlator threshold value, required before SFD
search. Note that on early CC2420 versions the reset value was
0.
5 DEMOD_AVG_MODE 0 R/W Frequency offset average filter behaviour.
0 : Lock frequency offset filter after preamble match
1 : Continuously update frequency offset filter.
4 MODULATION_MODE 0 R/W Set one of two RF modulation modes for RX / TX
0 : IEEE 802.15.4 compliant mode
1 : Reversed phase, non-IEEE compliant (could be used to set
up a system which will not receive 802.15.4 packets)
3:2 TX_MODE[1:0] 0 R/W Set test modes for TX
0 : Buffered mode, use TXFIFO (normal operation)
1 : Serial mode, use transmit data on serial interface, infinite
transmission. For lab testing only.
2 : TXFIFO looping ignore underflow in TXFIFO and read cyclic,
infinite transmission. For lab testing only.
3 : Send random data from CRC, infinite transmission. For lab
testing only.
1:0 RX_MODE[1:0] 0 R/W Set test mode of RX
0 : Buffered mode, use RXFIFO (normal operation)
1 : Receive serial mode, output received data on pins. Infinite
RX. For lab testing only.
2 : RXFIFO looping ignore overflow in RXFIFO and write cyclic,
infinite reception. For lab testing only.
3 : Reserved
RSSI (0x13) - RSSI and CCA Status and Control Register
Bit Field Name Reset R/W Description
15:8 CCA_THR[7:0] -32 R/W Clear Channel Assessment threshold value, signed number on
2’s complement for comparison with the RSSI.
The unit is 1 dB, offset is the same as for RSSI_VAL. The CCA
signal goes active when the received signal is below this value.
The CCA signal is available on the CCA pin.
The reset value is approximately -77 dBm.
7:0 RSSI_VAL[7:0] -128 R RSSI estimate on a logarithmic scale, signed number on 2’s
complement.
Unit is 1 dB, offset is described in the RSSI / Energy Detection
section on page 48.
The RSSI_VAL value is averaged over 8 symbol periods. The
RSSI_VALID
status bit may be checked to verify that the
receiver has been enabled for at least 8 symbol periods.
The reset value of –128 also indicates that the RSSI_VAL value
is invalid.