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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
56 of 1441
NXP Semiconductors
UM10503
Chapter 5: LPC43xx Boot ROM
5.3.2 Boot process for parts without flash
The top level boot process is illustrated in
. The boot starts after Reset is
released. The IRC is selected as CPU clock,the Cortex-M4 starts the boot loader, and
JTAG access is enabled.
As shown in
, the boot ROM determines the boot mode based on the OTP
BOOT_SRC value or reset state of the pins P1_1, P1_2, P2_8, and P2_9. The boot ROM
copies the image to internal SRAM at location 0x1000 0000 and jumps to that location (it
sets ARM's to 0x1000 0000) after image verification. Hence the images for LPC43xx
Fig 15. Boot process flowchart for LPC43xx parts with flash
CRP1/2/3 ENABLED?
yes
no
INITIALIZE
RESET
ENABLE DEBUG
check OTP/boot pins
USER CODE
VALID in FLASH
BANK A?
USER CODE
VALID in FLASH
BANK B?
yes
yes
CRP3 ENABLED?
Enter ISP
MODE?
(P2_7=LOW)
USER CODE VALID?
yes
yes
no
yes
no
no
no
no
A
A
EXECUTE INTERNAL
USER CODE
boot from external boot source
enter UART ISP if the boot source is USART0 or USART3