XE1205I074TRLF Просмотр технического описания (PDF) - Semtech Corporation

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XE1205I074TRLF

180 MHz – 1GHz Low-Power, High Link Budget Integrated UHF Transceiver

Semtech Corporation 

XE1205

The time diagram of an RSSI measurement is given in Figure 5. When the RSSI function has been activated the signal

strength is periodically measured and the result is stored in RSSI_out_int; this result is transferred to the register

RXParam_RSSI_out(1:0) each time this register is read via the SPI interface. TS_RSSI is the wake-up time required

after the function has been activated to get a valid result and its value is given in section 4.2.2. TS_RSSIM is the period

between two successive measurements and its value depends on the selected frequency deviation (100 μs for Δf > 20

kHz, 200 μs for 10 kHz < Δf ≤ 20 kHz, 300 μs for 7 kHz < Δf ≤ 10 kHz, 400 μs for 5 kHz < Δf ≤ 7 kHz, and 500 μs Δf ≤ 5

kHz).

RXParam_RSSI

NSS_CONFIG

RSSI_out_int

TS_RSSI

xxx

Read RSSI

TS_RSSIM

val1

val2

val3

saout_rssi

RXParam_RSSI_out

xxx

val1

Read RSSI

val4

0

val4

Figure 5: RSSI measurement timing diagram

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.

IRQParam_RSSI_int

RSSI_out_int

00 00 00 10 10 00 00 00 00 00 11 10 00 10 10 11 00

IRQParam_RSSI_signal_detect

IRQParam_RSSI_thr = “10”

RSSI_irq

Clear interrupt

Figure 6: RSSI generating interrupt signal when detecting a threshold

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