LPC540xx
NXP Semiconductors
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.
FRO
starts
FRO status
internal reset
V
DD
valid threshold
= 1.71 V
t
a
μs
t μs
b
GND
boot time
supply ramp-up
time
user code
t
c
μs
processor status
boot code
execution
finishes;
user code starts
aaa-024049
Fig 44. Start-up timing
Table 56. Typical start-up timing parameters
Parameter
Description
Value
ta
tb
FRO start time
20 s
151 s
Internal reset de-asserted
LPC540xx
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© NXP Semiconductors N.V. 2018. All rights reserved.
Product data sheet
Rev. 1.8 — 22 June 2018
144 of 168
NXP [ NXP ]
