2-6
Intel® PXA255 Processor
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
Section 3.4, “Resets and Power Modes” on page 3-6
.
•
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.
Table 2-4
shows each pin’s state after each
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
Sleep Mode
GPIO Reset
Watchdog Reset
Hard Reset
Core
reset
reset
reset
reset
Memory Controller
reset
preserved
reset
reset
LCD Controller
reset
reset
reset
reset
DMA Controller
reset
reset
reset
reset
Full Function UART
reset
reset
reset
reset
Bluetooth UART
reset
reset
reset
reset
Standard UART
reset
reset
reset
reset
Hardware UART
reset
reset
reset
reset
I
2
C
reset
reset
reset
reset
I
2
S
reset
reset
reset
reset
AC97
reset
reset
reset
reset
USB
reset
reset
reset
reset
ICP
reset
reset
reset
reset
RTC
preserved
preserved
reset (except RTTR)
reset
OS Timer
reset
reset
reset
reset
Содержание PXA255
Страница 1: ...Intel PXA255 Processor Developer s Manual January 2004 Order Number 278693 002 ...
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Страница 310: ...7 46 Intel PXA255 Processor Developer s Manual LCD Controller ...
Страница 330: ...8 20 Intel PXA255 Processor Developer s Manual Synchronous Serial Port Controller ...
Страница 358: ...9 28 Intel PXA255 Processor Developer s Manual I2 C Bus Interface Unit ...
Страница 488: ...13 36 Intel PXA255 Processor Developer s Manual AC 97 Controller Unit ...
Страница 572: ...16 30 Intel PXA255 Processor Developer s Manual Network SSP Serial Port ...
Страница 599: ...Intel PXA255 Processor Developer s Manual 17 27 Hardware UART ...
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