Datasheet

UM10398 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2014. All rights reserved.
User manual Rev. 12.3 — 10 June 2014 46 of 547
NXP Semiconductors
UM10398
Chapter 3: LPC111x/LPC11Cxx System configuration (SYSCON)
3.6 Reset
Reset has four sources on the LPC111x/LPC11Cxx: the RESET pin, Watchdog Reset,
Power-On Reset (POR), and Brown Out Detect (BOD). In addition, there is an ARM
software reset.
The RESET
pin is a Schmitt trigger input pin. Assertion of chip Reset by any source, once
the operating voltage attains a usable level, starts the IRC causing reset to remain
asserted until the external Reset is de-asserted, the oscillator is running, and the flash
controller has completed its initialization.
On the assertion of any reset source (ARM software reset, POR, BOD reset, External
reset, and Watchdog reset), the following processes are initiated:
1. The IRC starts up. After the IRC-start-up time (maximum of 6 s on power-up), the
IRC provides a stable clock output.
2. The flash is powered up. This takes approximately 100 s. Then the flash initialization
sequence is started.
3. The boot code in the ROM starts. The boot code performs the boot tasks and may
jump to the flash.
When the internal Reset is removed, the processor begins executing at address 0, which
is initially the Reset vector mapped from the boot block. At that point, all of the processor
and peripheral registers have been initialized to predetermined values.
3.7 Start-up behavior
See Figure 9 for the start-up timing after reset. The IRC is the default clock at Reset and
provides a clean system clock shortly after the supply voltage reaches the threshold value
of 1.8 V.