Texas Instruments 3138 155 232931 manual MDMCTRL1 0x12- Modem Control Register, RSSIVAL70

CC2420

MDMCTRL1 (0x12)– Modem Control Register 1

Bit	Field Name	Reset	R/W
15:11	-	0	W0
10:6	CORR_THR[4:0]	20	R/W
5	DEMOD_AVG_MODE	0	R/W
4	MODULATION_MODE	0	R/W
3:2	TX_MODE[1:0]	0	R/W

1:0 RX_MODE[1:0] 0 R/W

Description

Reserved, write as 0.

Demodulator correlator threshold value, required before SFD search. Note that on early CC2420 versions the reset value was 0.

Frequency offset average filter behaviour.

0 : Lock frequency offset filter after preamble match

1 : Continuously update frequency offset filter.

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)

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.

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
15:8	CCA_THR[7:0]	-32	R/W

7:0 RSSI_VAL[7:0] -128 R

Description

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.

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.

SWRS041B Page 65 of 89