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[FAQ] AM6442: MCU_RESETZ Reset input - connection of capacitor

Kallikuppa Sreenivasa
Guru**** 189649 points
Part Number: AM6442

Tool/software:

(Customer Query)

Hi TI Experts 

We are in progress for the Rev.B changes for the V2 SCC schematic and we have made few changes related to the reset circuit for which we need input/confirmation from TI.

 

  • In Rev A for MCU_RESETZ input we had provision for RC and Schmitt trigger
  • But for the Rev.B, based on customer feedback, we have eliminated the Schmitt trigger option and instead provided a pull up provision along with an optional capacitor provision for the MCU_RESETZ signal at the SOC side

 

Please refer to the attached snapshot of the implementation for Rev.A and Rev.B for the MCU_RESETZ.

 

We would appreciate your feedback on whether we can proceed with the current implementation.

Rev A

Rev B

  • 0
    TI__Guru**** 189649 points

    Hi Boatd Designers,

    Refer below

    Schmitt trigger based debouncing circuit (Rev A) is recommended if an RC or push button (slow ramp) is used.

    It is OK to use REVB if the cap is never populated. Customer could add a TP and connect an LVCMOS signal externally to reset.

    We do not allow slow ramp input (slew > 1000 ns ) to be applied to the LVCMOS inputs since the input could be driven in the mid supply region for certain time that can cause higher current flow and affect performance or reliability.

    The LVCMOS IOs should be operating above VIHSS or VILSS most of the time.

    This is valid for the RESET_REQz reset input also.

    Regards

    Sreenivasa

  • 0 in reply to Kallikuppa Sreenivasa
    Genius 4132 points

    Sreenvisa: I would make this an [FAQ] item please! The 3rd party SOM suppliers of AM6x products should also be alerted about this.

    later

    Jim

  • 0 in reply to Kallikuppa Sreenivasa
    TI__Guru**** 189649 points

    Hi Boatd Designers,

    Refer below:

    Purpose of the reset lines and reset outputs

    MCU_PORZ:  MCU and Main Domain cold reset.  This is the power-on reset for the MCU/entire device and is required.

    MCU_RESETZ:  MCU and Main Domain warm reset  This is the warm reset request for the MCU/entire device, optional. Pull-up if not used

    RESET_REQZ:  Main Domain external warm reset request input.  This is main domain warm reset request, optional.  Pull-up if not used

    Cold (power on reset) resets the entire device (all registers).  Warm reset reset most of the registers, but does not reset everything.  See TRM for definitions of which resets are NOT reset with warm reset.   Support for separate warm reset is optional.

    PORZ_OUT:  Power-On reset status output, simply buffered version of MCU_PORz input. 

    MCU_RESETSTATZ:  MCU Domain warm reset status output.  This the reset output of the MCU/entire device.  Is asserted for both external reset (MCU_PORz) and internal reset conditions (in the mcu domain).

    RESETSTATZ:  Main Domain warm reset status output, this reset output of the main domain, asserted for both external reset (MCU_PORz) and internal reset conditions (in the main domain).

    Which reset output to you for peripherals is design dependent.  If you want peripherals to reset only at power-up, the PORz_OUT.  If you want peripherals to reset at power-up and any time a internal processor reset is issued - then RESETSTATz.

    Connection of warm reset inputs for manual reset 

    Connectivity of WARM reset inputs when not used

    Refer to the pin connectivity requirements section of the processor-specific data sheet for connecting the warm reset inputs when not used.

    https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1403609/am6442-how-should-i-deal-with-b12-mcu_resetz-and-e18-reset_reqz-if-it-s-not-used/5415576?tisearch=e2e-sitesearch&keymatch=reset_reqz#5415576

    Regards,

    Sreenivasa