xe1205 Semtech Corporation, xe1205 Datasheet - Page 12

• Manufacturer Part Number: xe1205
• Description: Low-power, High Link Budget Integrated Uhf Transceiver
• Manufacturer: Semtech Corporation

Saout_rssi is internally generated during a read sequence of RXParam_RSSI_out register.
The RSSI block can also be used in interrupt mode by setting the bit IRQParam_RSSI_int to 1. When RSSI_out_int is
equal or greater than a predefined value stored in IRQParam_RSSI_thr(1:0), the signal IRQParam_RSSI_signal_detect
(can be read in the Configuration register) goes high and an interrupt signal RSSI_irq is generated. This interrupt signal
can be used by a microcontroller if IRQParam_RX_irq_0 is set to 01 (see table 5).The interrupt is cleared by writing a 1
to the bit IRQParam_RSSI_signal_detect. If the bit IRQParam_RSSI_int remains high, the process starts again. The next
figure shows the timing diagram of RSSI in interrupt mode.
5.2.3.5
The block is switched ON by writing bit RXParam_FEI to
of the local oscillator compared with the input carrier frequency and can be used to implement an external AFC. The
condition on the modulation index for proper behavior of the FEI function is:
Where Df is the frequency deviation and BR is the bit rate.
© Semtech 2007
b
IRQParam_RSSI_int
RSSI_out_int
IRQParam_RSSI_signal_detect
RSSI_irq
=
saout_rssi
NSS_CONFIG
RSSI_out_int
RXParam_RSSI_out
RXParam_RSSI
2
BR
D ×
f
Frequency Error Indicator in continuous mode
³
, 2
00
00
IRQParam_RSSI_thr = 10
Figure 6: RSSI generating interrupt signal when detecting a threshold
00
TS_RSSI
xxx
10
xxx
Figure 5: RSSI measurement timing diagram
10
00
val1
00
Read RSSI
00
Clear interrupt
12
.This function provides information about the frequency error
FEI
TS_RSSIM
00
val2
00
val1
11
val3
10
00
10
val4
Read RSSI
10
XE1205
val4
11
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00
0