Datasheet

LPC540xx All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet Rev. 1.8 — 22 June 2018 144 of 168
NXP Semiconductors
LPC540xx
32-bit ARM Cortex-M4 microcontroller
13. Application information
13.1 Start-up behavior
Figure 44 shows the start-up timing after reset. The FRO 12 MHz oscillator provides the
default clock at Reset and provides a clean system clock shortly after the supply pins
reach operating voltage.
Fig 44. Start-up timing
Table 56. Typical start-up timing parameters
Parameter Description Value
t
a
FRO start time 20 s
t
b
Internal reset de-asserted 151 s
aaa-024049
valid threshold
= 1.71 V
processor status
V
DD
FRO status
internal reset
GND
boot time
user code
boot code
execution
finishes;
user code starts
FRO
starts
supply ramp-up
time
t
b
µst
a
µs
t
c
µs