Samsung S5PC110, Manual

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S5PC110_UM 4 POWER MANAGEMENT
4-33
4.9 RESET CONTROL
4.9.1 RESET TYPES
S5PC110 has four types of resets and reset generator can place the system into one of five reset states.
There are five reset states, namely:
•
Hardware Reset - The hardware reset is generated when XnRESET is driven to low. It is an uncompromised,
ungated, and total reset that is used to drive S5PC110 to a known initial state.
•
Watchdog Reset - Reset signal by watchdog timer
•
Software Reset - Reset signal by setting special control register
•
Warm reset - Reset signal by XnWRESET pin.
•
Wakeup Reset - Reset signal generated when a module that has normal F/Fs is powered down, and the
module is powered up again by wakeup events; but in sleep mode, wakeup reset is generated to all modules
that were powered off regardless of normal F/F or retention F/F.
Five resets have the following priorities:
Hardware Reset > Watchdog Reset > Warm Reset > Software Reset > Wakeup Reset
4.9.2 HARDWARE RESET
Hardware reset is asserted when the XnRESET pin is driven to low, and all units in the system (except RTC
function module) are reset to known states.
During the hardware reset, the following actions take place:
•
All internal registers and Cortex-A8 go into their pre-defined reset state.
•
All pins get their reset state.
•
The XnRSTOUT pin is asserted when XnRESET is driven.
Hardware reset is asserted when an external source drives the XnRESET input pin low. XnRESET is non-
maskable, and therefore is always applicable. Upon assertion of XnRESET, S5PC110 enters into reset state
regardless of the previous state. For hardware reset to be asserted actually, XnRESET must be held long enough
to allow internal stabilization and propagation of the reset state.
Caution:
Power regulator for system must be stable prior to the deassertion of XnRESET. If power regulator for
system is not stable, it damages to S5PC110 and its operation is not guaranteed.