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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
99 of 1441
7.1 How to read this chapter
This chapter applies to LPC43Sxx parts (secure parts) only.
Flash-based, secure parts boot from on-chip flash by default (see
(secure) boot modes are also supported. The UART boot mode is only supported for
flashless parts. The secure boot from USART3 is not supported for LPC43Sxx parts.
7.1.1 Determine the boot code version
For parts with on-chip flash, the boot code version can be determined using ISP or IAP
calls. See
Table 47 “ISP Read Boot Code version number command”
and
Read Boot Code version number command”
.
For flashless parts, use ISP to read the boot code version number (see
) or read
memory location 0x1040 7FFC which encodes the boot code version as follows:
Value 0x000B 000n at location 0x1040 7FFC reads as boot code version 11.n.
7.2 Features
•
Secure booting from an encrypted image.
•
Cypher-based Message Authentication Code (CMAC) authentication on the boot
image.
•
Supports development mode for booting from a plain text image. Development mode
is terminated by programming the AES key.
7.3 Functional description
7.3.1 Boot sources
The boot source is defined by the OTP or, if the OTP is blank, by the state of the boot pins
in the same way as for non-secure parts. Secure parts with and without internal flash
support the same boot sources as non-secure parts. See
7.3.2 Encryption and boot flow
All flashless secure parts can boot from a secure (encrypted) image with CMAC
authentication. For parts with on-chip flash, the ISP mode must be enabled to select an
external boot source with the encrypted image.
Remark:
Any on-chip flash image containing valid user code can be protected by
selecting from several CRP levels. See
Section 6.6 “Code Read Protection (CRP)”
.
Secure booting generally involves the following steps:
1. On an external device, create a secure image from the plain-text image:
UM10503
Chapter 7: LPC43Sxx Boot ROM for secure parts
Rev. 2.1 — 10 December 2015
User manual