Pin conditions during ST bootloader selection

[Kai4]

Hello everybody,

for first time flash programming of private CAN bootloader i want to use the ST bootloader.
Despite of the nBoot_SEL Bit i can flash data if the flash is empty.
The bootloader mechanism is shown in Figure 55 in the AN2606.
Now the questions :

1. Do i have to set valid level for e.g the RXD pins of UART 1 and 2 and 3 or are the internal pullup R used ?

2 During scan of all possible interfaces, see Fig. 55 in AN2606, are the corresponding output pins (e.g. TXD pins) of the interfaces in Tri-state ?
E.g. UART3 is used for flash update, is it possible to use TXD of UART2 for input, that means an external driver circuit
drives into TXD of UART2 ?

3. If i use FDCAN, do i have to use FDCAN1 (PD0 and PD1, AN2606, Table95) or FDCAN2 (Manual, 2.5, page68, pins ?) ?

Thanks in advance,

BR, Kai

[TDK · Accepted solution]

1. If you want to use the interface, you should be driving that pin. Pullups shouldn't be needed. If you don't want to use the interface, no action is necessary, but you should take care to ensure the pins do not jitter.

2. Generally they are in high impedance mode until that particular interface is driven. It's not specified by ST. I would double check the behavior for your particular chip, but it should be fine.

3. Supported interfaces are given in AN2606. Pins PD0/PD1.

[Kai4]

HI TDK,

thanks for your answers.
I will check all possible input pins (RXD, MOSI, I2C-Pins).

BR.