AN3154 datasheet(6/34 Pages) STMICROELECTRONICS

6 / 34 page

Bootloader code sequence

AN3154

6/34

DocID017063 Rev 5

Figure 2. Check HSE frequency

1. For some devices, the HSE frequency is calculated using HSI oscillator connected to a timer. For other

devices, this measurement is not implemented. For the devices without HSE frequency measurement, only

the flow represented on the left is executed, while for the devices with HSE frequency measurement, only

the flow on the right is executed. To know which flow is relative to your device, please refer to AN2606.

Start check HSE frequency

Configure external Oscillator mode

(System Clock = 60 MHz)

Initialize timeout at ~3 ms

Generate System Reset

Enter an infinite loop, waiting for any

CAN bootloader command.

Configure CAN baudrate at 125 Kbps

Assuming that HSE = 8 MHz

Initialize timeout at ~1.5 ms

Message

received with stdID=0x79

and without frame error?

Yes

Configure CAN baudrate at 125Kbps

Assuming that HSE = 25MHz

Initialize timeout at ~1.5 ms

Message

received with stdID=0x79

and without frame error

Yes

Configure CAN baudrate at 125Kbps

Assuming that HSE = 14.7456MHz

Initialize timeout at ~1.5 ms

Message

received with stdID=0x79

and without frame error

Yes

HSE measured with HSI

and Timer

(1)

No HSE measurement

(1)

Message

received with stdID=0x79

and without frame error

Yes

Generate System Reset

ai15704c

Decrement timeout

Timeout = 0x0 ?

Decrement timeout

Timeout = 0x0 ?

Decrement timeout

Timeout = 0x0 ?

Yes

Decrement timeout

Timeout=0x0?

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