Si1000/1/2/3/4/5
an incorrect error may rarely occur. The RSSI value may be incorrect if read during the update period. The
update period is approximately 10 ns every 4 Tb. For 10 kbps, this would result in a 1 in 40,000 probability
that the RSSI may be read incorrectly. This probability is extremely low, but to avoid this, one of the follow-
ing options is recommended: majority polling, reading the RSSI value within 1 Tb of the RSSI interrupt, or
using the RSSI threshold described in the next paragraph for Clear Channel Assessment (CCA).
D7
D6
D5
D4
D3
D2
D1
D0
POR
Def.
Add R/W
Function/Description
26
27
R
Received Signal Strength Indicator
rssi[7]
rssi[6]
rssi[5]
rssi[4]
rssi[3]
rssi[2]
rssi[1]
rssi[0]
—
R/W RSSI Threshold for Clear Channel Indicator rssith[7] rssith[6] rssith[5] rssith[4] rssith[3] rssith[2] rssith[1] rssith[0]
00h
For CCA, threshold is programmed into rssith[7:0] in "Register 27h. RSSI Threshold for Clear Channel
Indicator." After the RSSI is evaluated in the preamble, a decision is made if the signal strength on this
channel is above or below the threshold. If the signal strength is above the programmed threshold then the
RSSI status bit, irssi, in "Register 04h. Interrupt/Status 2" will be set to 1. The RSSI status can also be
routed to a GPIO line by configuring the GPIO configuration register to GPIOx[3:0] = 1110.
RSSI vs Input Power
250
200
150
100
50
0
-120
-100
-80
-60
-40
-20
0
20
In Pow [dBm]
Figure 23.25. RSSI Value vs. Input Power
23.9. Reference Design
Reference designs are available at www.silabs.com for many common applications which include recom-
mended schematics, BOM, and layout. TX matching component values for the different frequency bands
can be found in the application notes “AN435: Si4032/4432 PA Matching” and “AN436:
Si4030/4031/4430/4431 PA Matching.” RX matching component values for different frequency bands can
be found in “AN427: EZRadioPRO Si433x and Si443x RX LNA Matching.”
280
Rev. 1.0
SILICON [ SILICON ]
