UM10503
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© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1.3 — 6 July 2012
36 of 1269
NXP Semiconductors
UM10503
Chapter 5: LPC43xx Boot ROM
[1]
The boot loader programs the appropriate pin function at reset to boot from SPIFI or SSP0.
5.3.1 Boot process
The top level boot process is illustrated in
. The boot starts after Reset is
released. The IRC is selected as CPU clock and the Cortex-M4 starts the boot loader. By
default the JTAG access to the chip is disabled at reset. When the part is non-AES
capable or it is AES capable but the AES key has not been programmed then 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 shadow pointer to 0x1000 0000) after image verification. Hence the images
for LPC43xx should be compiled with entry point at 0x0000 0000. On AES capable
LPC43xx with a programmed AES key the image and header are authenticated using the
CMAC algorithm. If authentication fails the device is reset.
On AES capable LPC43xx in development mode and non-AES capable LPC43xx, the
image and header are not authenticated. If the image is not preceded by a header then
the image is not copied to SRAM but assumed to be executable as-is. In that case the
shadow pointer is set to the first address location of the external boot memory. The
header-less images for LPC43xx should be compiled with entry point at 0x0000 0000, the
same as for an image with header.
Remark:
When the boot process fails, pin P1_1 toggles at a 1 Hz rate for 60 seconds.
After 60 seconds, the device is reset.
USB1
LOW
HIGH
HIGH LOW
Boot
from
USB1.
SPI (SSP)
LOW
HIGH
HIGH
HIGH
Boot from SPI flash connected to the SSP0 interface on P3_3
(function SSP0_SCK), P3_6 (function SSP0_MISO), P3_7
(function SSP0_MOSI), and P3_8 (function SSP0_SSEL)
USART3
HIGH
LOW
LOW
LOW
Boot from device connected to USART3 using pins P2_3 and
P2_4. For flash parts, enter UART ISP mode.
Table 19.
Boot mode when OTP BOOT_SRC bits are zero
Boot mode
P2_9
P2_8
P1_2
P1_1
Description