I have a question about designing st-link v2. According to the schematics provided by st.com Please help me in analyzing this schematic. Why boot0 was pulldown with a 100k resistor but connected boot1 without GND resistor.

According to the AN2586, the pin boot0 and boot1 must be connected to a VCC or GND 10k resistor. But this point is not met

enter image description here


1 Answer 1


Right below Figure 10 of AN2586 it mentions:

Resistor values are given only as a typical example.

These pins can be tied directly to VDD or GND, but it is common practice to use resistors for a few reasons.

  1. Series resistors can provide some current-limiting protection to the microcontroller pins.

  2. Putting at least one resistor between the pin and VDD/GND allows for easier rework if the initial design assumptions/requirements change (e.g. oh no, we want to boot from system memory now instead of main FLASH memeory!).

  3. Adding resistors to both VDD and GND -- and not populating one of them -- allows for switching between boot configurations with only a bill of materials (BOM) change instead of rerouting a PCB in order to achieve this.

  • \$\begingroup\$ Thank you very much for your answer. \$\endgroup\$
    – mojtaba
    Commented May 23, 2019 at 19:30

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