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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
104 of 571
NXP Semiconductors
UM10316
Chapter 10: LPC29xx general system control
Setting the power mode and configuring the clock domains is handled by the CGU, see
. Configuration of wake-up events is handled by the Event Router, see
4.
Reset and power-up behavior
The LPC29xx contains external reset input and internal power-up reset circuits. This
ensures that a reset is internally extended internally until the oscillators and flash have
reached a stable state.
At activation of the RSTN pin the JTAGSEL pin is sensed as logic LOW. If this is the case
the LPC29xx is assumed to be connected to debug hardware, and internal circuits
re-program the source for the BASE_SYS_CLK to be the crystal oscillator instead of the
Low-Power Ring Oscillator (LP_OSC). This is required because the clock rate when
running at LP_OSC speed is too low for the external debugging environment.
5.
Functional description of the interrupt and wake-up structure
An overview of the interrupt and wake-up structure is given in
. The main
functions are:
•
Events and interrupt requests causing an interrupt (IRQ or FIQ) on the ARM
processor.
•
Events and interrupt requests causing a wake-up. During low-power mode selected
clock domains are switched off, and they are turned on by this wake-up.
In this case the VIC (Vectored Interrupt Controller) is configured to send an interrupt (IRQ
or FIQ) towards the ARM processor. Examples are interrupts to indicate the reception of
data via a serial interface, or timer interrupts. The Event Router serves as a multiplexer for
internal and external events and indicates the occurrence of such an event towards the
VIC (Event-Router interrupt). The Event Router is also able to latch the occurrence of
these events (level or edge-triggered).
Table 92.
Reset pin
Symbol
Direction
Description
RSTN
in
external reset input, active LOW; pulled up internally
Fig 21. Interrupt and wake-up structure
Event
Router
CGU
VIC
ARM
IRQ
FIQ
...
UART
...
...
wake-up
Interrupt Requests
Events
Ext.
Int.