SPRUIU1C July 2020 – February 2024 DRA821U , DRA821U-Q1
RESET_REQz release requires:
RESET_REQz must be held active (low) for a minimum of 1.2 µs.
Like the PORz sequence, it is necessary to have configured CTRLMMR_WKUP_MAIN_WARM_RST_CTRL[0] SOC_WARMRST_ISO_DONE_Z high in order to block the reset request from immediately propagating. Unlike the PORz sequence, there is no timeout. Also, unlike the PORz sequence, some clock domains within given power domains can be configured to ignore the RESET_REQz signal.
As an example of how to read tables in the PSC: Device Power-Management Layout Section, in Power, PSC0 Power Management Device-Level Layout shows that PD_R5FSS_0 is assigned Power Domain Index 24 with LPSCs 93, 94, and 95 controlling clocks/resets to circuitry within this power domain. PSC0 Power Domain Features shows that power domain 24 is OFF by default (if isolation does not block the reset). PSC0 LPSC Features shows that LPSC 93, 94, and 95 are OFF by default but LPSC 93 and 94 can be configured for reset isolation.
If Reset isolation is selected for LPSC 93 and 94, resets and clocks are not affected by the RESET_REQz signal. Power Domain 24 cannot be reset when the LPSCs are active. Note that LPSC 95 is reset.
If Reset isolation is not selected for either LPSC 93 or 94, resets propagate to LPSC 93, 94, and 95; the clocks are stopped to these LPSCs (since their default state is OFF). Power Domain 24 is reset to its OFF state.
At the end of this sequence, MCU_R5FSS0 can read the CTRLMMR_WKUP_MAIN_WARM_RST_CTRL[0] SOC_WARMRST_ISO_DONE_Z bit and begin re-configuring the MAIN domain.
On warm resets (except those caused by a VTM Thermal over-temperature), the output of various PLLs are either bypassed or left unaffected. For more details, see Section 5.3.7, PLL Behavior on Reset.