Reset; Effect Of Each Type Of Reset On Internal Register State - Intel PXA255 Developer's Manual

System Architecture
Each interrupt goes through the Interrupt Controller Mask Register and then the Interrupt
Controller Level Register directs the interrupt into either the IRQ or FIQ. If an interrupt is taken,
the software may read the Interrupt Controller Pending Register to identify the source. After it
identifies the interrupt source, software is responsible for servicing the interrupt and clearing it in
the source unit before exiting the service routine.
Note: Clearing interrupts may take a delay. To allow the status bit to clear before returning from an
interrupt service routine (ISR), clear the interrupt early in the routine.
2.6

Reset

The processor can be reset in any of three ways: Hardware, Watchdog, and GPIO resets. Each is
described in more detail in
•
Hardware reset results from asserting the nRESET pin and forces all units into reset state.
•
Watchdog reset results from a time-out in the OS Timer and may be used to recover from
runaway code. Watchdog reset is disabled by default and must be enabled by software.
•
GPIO reset is a "soft reset" that is less destructive than Hardware and Watchdog resets.
Each type of reset affects the state of the processor pins.
type of reset.
Leaving Sleep Mode causes a Sleep Mode reset. Unlike other resets, Sleep Mode resets do not
change the state of the pins.
The Reset Controller Status Register (RCSR) contains information on the type of reset, including
Sleep Mode resets.
Table 2-4. Effect of Each Type of Reset on Internal Register State (Sheet 1 of 2)
Unit
Core
Memory Controller
LCD Controller
DMA Controller
Full Function UART
Bluetooth UART
Standard UART
Hardware UART
2
I C
2
I S
AC97
USB
ICP
RTC
OS Timer
2-6
Section 3.4, "Resets and Power Modes" on page
Sleep Mode
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
preserved preserved
reset
Table 2-4
GPIO Reset
reset reset
preserved reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset reset
reset (except RTTR)
reset reset
Intel® PXA255 Processor Developer's Manual
3-6.
shows each pin's state after each
Watchdog Reset Hard Reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset
reset