SX1232
WIRELESS & SENSING
DATASHEET
4.3. Receiver Startup Options
The SX1232 receiver can automatically control the gain of its receiver chain (AGC) and adjust its receiver LO frequency
(AFC). Those processes are carried out on a packet-by-packet basis, and they occur:
when the receiver is turned On
when the Receiver is restarted upon user request, through the use of trigger bits RestartRxWithoutPllLock or
RestartRxWithPllLock, in RegRxConfig.
when the receiver is automatically restarted after the reception of a valid packet, or after a packet collision.
Automatic restart capabilities are detailed in section 4.4.
Several receiver startup options are offered in the state machine of the SX1232, and they are described in Table 22:
Table 22 Receiver Startup Options
Triggering Event Realized Function AgcAutoOn
AfcAutoOn
RxTrigger
(2:0)
None
None
AGC
0
1
1
1
1
1
1
0
0
1
0
1
0
1
000
001
001
110
110
111
111
Rssi Interrupt
AGC & AFC
AGC
PreambleDetect
AGC & AFC
AGC
Rssi Interrupt
&
PreambleDetect
AGC & AFC
When AgcAutoOn=0, the LNA gain is manually selected by choosing LnaGain bits in RegLna.
4.4. Receiver Restarting Methods
It may be useful to restart the receiver, for example to prepare for the reception of a new signal whose strength may widely
differ from the previous packet receiver, or whose carrier frequency may be different, required a new AFC. A few options
are proposed:
4.4.1. Restart Upon User Request
At any point in time, when the device is in Receive mode, the user can restart the receiver; this is particularly useful in
conjunction with the use of a Timeout, whereby the receiver would need restarting if it had not detected any incoming
packet after a few milliseconds of channel scanning. Two options are available:
No change in the Local Oscillator upon restart: the AFC is disabled, and the Frf register has not been changed through
SPI before the restart instruction: set bit RestartRxWithoutPllLock in RegRxConfig to 1.
Local Oscillator change upon restart: if AFC is enabled (AfcAutoOn=1), and/or the Frf register had been changed during
the last Rx period: set bit RestartRxWithPllLock in RegRxConfig to 1.
Note ModeReady must be at logic level 1 for a new RestartRx command to be taken into account
Rev 3 - August 2012
Page 42
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