Boot; Standby; Figure 2-2: Bootloader; Table 2-1: Setstandby Command - Semtech LR1121 User Manual

2.1.1 Boot

The bootloader is the first piece of software executed after power-on reset, and is located at the beginning of flash memory.
The detailed description in AN1200.57 LR1110 Program Memory Update applies to all LR11xx devices.
Two main tasks are assigned to the bootloader:
• The first task checks if a valid firmware is loaded before jumping there.
• The second task loads a firmware: it receives encrypted chunks of data sent through the SPI and performs an on-the-fly
decryption before writing data in flash.
Flash

2.1.2 Standby

This is the default mode of the LR1121. It is the return state from all other modes (except for specific fall-back options), and
the mode from which transitions to other modes are possible. All commands to configure the device should be issued in
this mode.
Two clocks are available: either the internal 32MHz RC oscillator (Standby RC mode), or an external 32MHz crystal/TCXO
(Standby Xosc mode). The RC clock is used by default for all automatic mode transitions. The crystal/TCXO clock allows
faster transitions to other modes at the expense of a higher power consumption.
2.1.2.1 SetStandby
Command SetStandby(...) sets the device in standby mode with the chosen 32MHz oscillator.

Table 2-1: SetStandby Command

Byte
Data from Host
Data to Host
StdbyConfig selects the oscillator used in standby mode:
•
0x00: Selects internal RC oscillator (Standby RC mode)
•
0x01: Selects external Xtal/TCXO oscillator (Standby Xosc mode)
LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
Bootloader
Firmware

Figure 2-2: Bootloader

0
0x01
Stat1
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The program starts here, then...
... jumps here!
1
0x1C
Stat2
2
StdbyConfig
IrqStatus(31:24)
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