UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
1171 of 1269
NXP Semiconductors
UM10503
Chapter 46: LPC43xx flash programming/ISP and IAP
46.4.3 Boot process for parts with internal flash
If pin P2_7 is sampled LOW, the boot loader checks the OTP bits and/or the external boot
pins to determine the communication port. If the OTP bits and boot pins are set to
USART0 or USART3, the part enters UART ISP mode.
A boot image must have a valid signature to be a valid flash image (see
),
and on parts with dual flash banks, only one flash bank should contain a valid image. You
can use the ISP/IAP command Set active boot flash bank to configure one flash bank with
the valid image (see
and
). If both images are valid, the
boot loader loads the image located in flash bank A.
Fig 175. Boot process flowchart for LPC43xx parts with flash
WATCHDOG
FLAG SET?
CRP1/2/3 ENABLED?
yes
no
INITIALIZE
RESET
ENABLE DEBUG
yes
check OTP/boot pins
USER CODE
VALID in FLASH
BANK A?
USER CODE
VALID in FLASH
BANK B?
yes
yes
no
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