Chapter 03 Power, Reset, and Clock Management.pdf

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PRCM Functional Description www.ti.com
• Scope
• Occurrence
• Source type
3.5.1.2.1 Scope
A reset signal can be categorized according to its scope (the area of the device affected by that reset):
• Global reset: Affects the entire device; all modules are reset. Generally, occurs when the device
powers up or an abnormal operation is detected (the eFuse bad device is detected, etc.).
• Local reset: Affects one power or reset domain. Generally, when a power domain transitions from off
mode to active mode, or when a software-reset control bit for a domain is set, only the group of
modules within that domain is affected.
3.5.1.2.2 Occurrence
A reset signal can be categorized depending on when the reset occurs:
• Cold reset: Occurs only on device power up or in certain emulation modes. The cold reset is a global
reset that affects every module in the device. It usually corresponds to the initial power-on reset.
• Warm reset: Occurs when the device is in normal operating state. The warm reset is also a global
reset, but it does not affect all the modules in the device. Usually, the device does not require a
complete reboot on a warm reset. Several reset sources, such as the global software reset and the
watchdog reset, are warm resets.
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.
For a global warm reset, the PRCM module performs the following sequence:
1. Applies a warm reset on all the modules, including modules built with RFFs.
2. Applies a warm reset on the external modem interface.
3. Drives the sys_nreswarm reset output low and holds it for a specified length of time (programmed in
the PRCM.PRM_RSTTIME[7:0] RSTTIME1 bit field).
4. All ongoing transactions on the voltage control I 2 C interface (I2C4 module) are aborted, and the
external power IC is expected to return to nominal voltage values on receiving a sys_nreswarm reset.
5. All power domains that are in off power mode are switched to on power mode.
A global warm reset does not apply to the following modules of the device:
• SDRC
• System control module (SCM) (I/O control)
• Part of PRM and CM registers (see note below)
• 32-kHz synchronization timer
• DPLL3 (see Section 3.5.1.9.2)
• Emulation modules
• eFuse farm
NOTE: For information about the PRCM registers affected by the global warm reset, see the
register mapping summary tables in Section 3.7, PRCM Register Manual.
3.5.1.2.3 Source Type
A reset can be categorized depending on whether it is software-controlled or hardware-triggered:
• Software reset: Triggered by setting a bit in a configuration register of the PRCM module
• Hardware reset: Triggered by a signal from a hardware module inside or outside the PRCM module
3.5.1.3 Reset Sources
Figure 3-21 is an overview of the reset sources.
250 Power, Reset, and Clock Management SPRUGN4L–May 2010–Revised June 2011
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