STM32F303x - Hardware Resets

[gbigden]

Posted on February 09, 2015 at 15:51

What is the usual procedure for power-on reset for other chips besides the MCU? Is there a reset_out signal or method coming from the MCU that is recommended? Or is there a method for resetting all chips in a system including the MCU?

#reset-stm32

[ivani]

Posted on February 09, 2015 at 16:54 There could be several solutions: - the most simple - wire all reset pins (including MCU) to a common power-on-reset chip - use one (or sometimes more) MCU I/O pins as reset signals for other chips - this gives you the flexibility to reset the other chips at any time if something goes totally wrong (or to reinitialize them to a defined state).

[waclawek.jan]

Posted on February 09, 2015 at 17:11

>  Is there a reset_out signal or method coming from the MCU that is recommended?

See Fig.11 ''Simplified diagram of the reset circuit'' in RM0316. Unfortunately, the diagram in datasheet and related timing data do not reflect the bidirectional character of the pin. JW

[gbigden]

Posted on February 09, 2015 at 17:13

But if I just pull NRST low and then high that should do for the MCU reset?

[Tesla DeLorean]

Posted on February 09, 2015 at 17:47

The NRST/NRESET pin in ARM designs is generally considered as bi-directional. You can reset the CPU and all the peripherals (internal/external), both with external reset circuit(s) and by the processor (core via NVIC). Some of the causes can also be read from a register post reset.

You can supply your own power-on-reset circuits, including ones that monitor multiple supplies, and ensure sequencing, thresholding, etc. The one thing you must be very careful of is not to drive NRESET high with a push-pull driver, this will prevent the part from correctly resetting.

[gbigden]

Posted on February 10, 2015 at 18:15

The one thing you must be very careful of is not to drive NRESET high with a push-pull driver, this will prevent the part from correctly resetting.

Big thanks for that! I just changed the supervisor reset from PP to OC...

[Tesla DeLorean]

Posted on February 10, 2015 at 18:32

Big thanks for that! I just changed the supervisor reset from PP to OC...

You're not the first one to have done that, it's a big trap and lots of people fall in it.