SWRS046I November 2006 – September 2018 CC1020
PRODUCTION DATA.
The carrier sense signal is based on the RSSI value and a programmable threshold. The carrier sense function can be used to simplify the implementation of a CSMA (Carrier Sense Multiple Access) medium access protocol.
Carrier sense threshold level is programmed by CS_LEVEL[4:0] in the VGA4 register and VGA_SETTING[4:0] in the VGA3 register.
VGA_SETTING[4:0] sets the maximum gain in the VGA. This value must be set so that the ADC works with optimum dynamic range for a certain channel filter bandwidth. The detected signal strength (after the ADC) will therefore depend on this setting.
CS_LEVEL[4:0] sets the threshold for this specific VGA_SETTING[4:0] value. If the VGA_SETTING[4:0] is changed, the CS_LEVEL[4:0] must be changed accordingly to maintain the same absolute carrier sense threshold. See Figure 5-15 for an explanation of the relationship between RSSI, AGC and carrier sense settings.
The carrier sense signal can be read as the CARRIER_SENSE bit in the STATUS register.
The carrier sense signal can also be made available at the LOCK pin by setting LOCK_SELECT[3:0] = 0100 in the LOCK register.