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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
55 of 1441
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.
Remark:
Pin functions for SPIFI and SSP0 boot are different.
5.3.1 Boot process for parts with internal flash
Parts with flash boot from on-chip flash if PIO2_7 is sampled HIGH. See
.
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
“Criterion for Valid User Code”
), 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
). If both images are valid, the boot loader loads the image located in flash
bank A.
Remark:
If the boot loader image is located in flash bank B and data is stored in flash
bank A, then ensure that the data in flash bank A does not appear to be a valid image. An
example of a data set that would be interpreted as a valid image is a set in which the first
eight words of flash bank A contain all zeros.
This implies that the data in the first 8 locations of sector 0 in flash bank A cannot be
chosen freely. For example, choose data in location 8 in such a way that a non-valid
image is created. See
Section 6.4.4.1 “Criterion for Valid User Code”
Table 22.
Boot mode when OTP BOOT_SRC bits are zero
Boot mode
P2_9
P2_8
P1_2
P1_1
Description
USART0
LOW
LOW
LOW
LOW
Boot from device connected to USART0 using pins P2_0 and
P2_1. For flash parts, enter UART ISP mode.
SPIFI
LOW
LOW
LOW
HIGH
Boot from Quad SPI flash connected to the SPIFI interface on
P3_3 to P3_8
EMC 8-bit
LOW
LOW
HIGH
LOW
Boot from external static memory (such as NOR flash) using CS0
and an 8-bit data bus.
EMC 16-bit
LOW
LOW
HIGH
HIGH
Boot from external static memory (such as NOR flash) using CS0
and a 16-bit data bus.
EMC 32-bit
LOW
HIGH
LOW
LOW
Boot from external static memory (such as NOR flash) using CS0
and a 32-bit data bus.
USB0
LOW
HIGH LOW
HIGH
Boot
from
USB0.
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_SSEL), P3_7
(function SSP0_MISO), and P3_8 (function SSP0_MOSI)
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. The secure boot
from USART3 is not supported for LPC43Sxx parts.