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 applies to parts LPC2458, LPC2468, and LPC2478.

The Boot Loader controls initial operation after reset, and also provides the means to 
accomplish programming of the Flash memory. This could be initial programming of a 
blank device, erasure and re-programming of a previously programmed device, or 
programming of the Flash memory by the application program in a running system.

In-System Programming: In-System programming (ISP) is programming or 
reprogramming the on-chip Flash 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 Flash memory, as directed by the end-user 
application code.

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

The Flash 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.

Pin P2.10 that is used as hardware request for ISP requires special attention. Since P2.10 
is in high impedance mode after reset, it is important that the user provides external 
hardware (a pull-up resistor or other device) to put the pin in a defined state. Otherwise 
unintended entry into ISP mode may occur.