Nxp Semiconductors UM10237 ユーザーズマニュアル

UM10237_2

© NXP B.V. 2008. All rights reserved.

 

Remark: This chapter describes the boot process for flashless parts LPC2420/60 and 
LPC2470. It does not apply to parts LPC2458, LPC2468, and LPC2478.

The on-chip bootloader version 3.4 controls the boot process for flashless LPC2400 parts 
LPC2420/60 and LPC2470. 

In-System Programming: In-System programming (ISP) is programming or 
reprogramming the on-chip memory, using the boot loader software and UART0 serial 
port. This can be done when the part resides in the end-user board.

In Application Programming: In-Application (IAP) programming is performing erase 
and write operation on the on-chip memory, as directed by the end-user application 
code.

The boot loader provides both In-System and In-Application programming interfaces for 
programming the on-chip memory.

The bootloader is designed as a tool that enables the user to load system specific 
application for further programming of in system available off-chip Flash and/or RAM 
resources. The bootloader itself does not contain any external memory programming 
algorithms. The bootloader implemented in LPC2460/70 supports a limited set of 
commands dedicated to code download and its execution from on-chip RAM only. UART0 
is the sole serial channel the boot loader can use for data download. Although a fractional 
divider is available in the UART0, it is not used by the on-chip bootloader.

The boot loader code is executed every time the part is powered on or reset. The loader 
can execute the ISP command handler or the user application code. A LOW level after 
reset at the P2.10 pin is considered as an external hardware request to start the ISP 
command handler. Assuming that power supply pins are on their nominal levels when the 
rising edge on RESET pin is generated, it may take up to 3 ms before P2.10 is sampled 
and the decision on whether to continue with user code or ISP handler is made. If P2.10 is 
sampled low and the watchdog overflow flag is set, the external hardware request to start 
the ISP command handler is ignored. If there is no request for the ISP command handler 
execution (P2.10 is sampled HIGH after reset), a search is made for a valid user program. 
If a valid user program is found then the execution control is transferred to it. If a valid user 
program is not found, the auto-baud routine is invoked.