UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 34 of 792
NXP Semiconductors UM10237
Chapter 3: LPC24XX System control
The various Resets have some small differences. For example, a Power On Reset causes
the value of certain pins to be latched to configure the part.
For more details on Reset, PLL and startup/boot code interaction see Section 4–3.2.2
PLL and startup/boot code interaction.
3.2.1 Reset Source Identification Register (RSIR - 0xE01F C180)
This register contains one bit for each source of Reset. Writing a 1 to any of these bits
clears the corresponding read-side bit to 0. The interactions among the four sources are
described below.
Fig 11. Example of start-up after reset
valid threshold
processor status
VDD(3V3)
IRC status
RESET
GND
002aad482
30 μs1 μs; IRC stability count
8 μs170 μs160 μs
boot time user code
boot code
execution
finishes;
user code starts
IRC
starts IRC
stable
flash read
finishes
flash read
starts
supply ramp-up
time