A reset signal can be categorized depending on when the reset occurs:
- Cold reset: Occurs on device power up (POR), or in certain emulation modes. Also, it can be software-initiated. Upon cold reset, it is assumed the device is being powered up, and therefore, everything in the device is being reset. That is, cold resets must be considered as global resets.
- Warm reset: Warm reset types are not necessarily applied globally within device. Also, a module can use a warm reset to reset a subset of its logic. This is often done to speed up reset recovery time; that is, the time to transition to a safe operating state, compared to the time required upon receipt of a cold reset. Warm reset events include software-triggered reset per power domain, watchdog time-out, externally triggered and emulation initiated.
Modules that behave differently in cold reset and warm reset have two reset signals: RST and PWRON_RST. These reset signals reconstruct warm reset and cold reset in modules that require them.
The following modules are reset upon global cold reset events and not upon global warm reset events:
- All DPLLs associated with the PRCM module
- EMIF
- Control module: CTRL_MODULE_CORE, CTRL_MODULE_WKUP
Note: The DPLLs state will change after warm reset even though they are not warm reset-sensitive, refer to Section 3.5.6.18, Global Warm Reset Sequence for more details.
Note: For information about the PRCM module registers affected by the global warm reset, see the register description in Section 3.13, PRCM Register Manual.