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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
66 of 1441
NXP Semiconductors
UM10503
Chapter 5: LPC43xx Boot ROM
5.3.6 UART ISP
In-System programming (ISP) is programming or re-programming the on-chip SRAM
memory using the boot loader software and the USART0 serial port. For flash parts,
USART3 is available for ISP communication as well (see
). ISP can
be performed when the part resides in the end user board.
A LOW level on pin P2_7 after reset indicates hardware request to enter ISP mode.
ISP commands include preparing the on-chip flash for erase and write operation, reading,
writing, and erasing flash, and executing code from flash. For flashless parts, a limited set
of ISP commands is supported which allows to load data into on-chip SRAM and execute
code from on-chip SRAM. For details, see
Fig 22. Boot process timing
GND
VDDREG
IRC12
RESET
supply
ramp up
IRC12
starts
IRC12
stable
22 μs
0.5μs; IRC stability count
valid
threshold
boot time
user code
processor status
t
a
μs
t
b
μs
t
c
μs
check boot
selection
pins
copy image to
embedded
SRAM
initialise
device