UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 616 of 841
32.1 Introduction
The boot loader controls initial operation after reset and also provides the tools for
programming 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.
32.2 Features
• 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.
• Flash signature generation: built-in hardware can generate a signature for a range of
flash addresses, or for the entire flash memory.
32.3 Description
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 pin P2.10 is considered 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 is used as a hardware request signal for ISP and therefore 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.
When ISP mode is entered after a power on reset, the IRC and PLL are used to generate
the CCLK of 14.748 MHz. The baud rates that can easily be obtained in this case are:
9600 baud, 19200 baud, 38400 baud, 57600 baud, 115200 baud, and 230400 baud. This
may not be the case when ISP is invoked by the user application (see Section 32.8.9
“Re-invoke ISP” on page 637).
UM10360
Chapter 32: LPC176x/5x Flash memory interface and
programming
Rev. 3 — 19 December 2013 User manual
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