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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
68 of 1441
NXP Semiconductors
UM10503
Chapter 6: LPC43xx/LPC43Sxx flash programming/ISP and IAP
•
Flash signature generation: built-in hardware can generate a signature for a range of
flash addresses or for the entire flash memory.
6.4 General description
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.
Remark:
The initial value of the flash memory and the memory value after an erase
operation is all 1s.
The boot loader code is executed every time the part is powered on or reset. The boot
loader can execute the ISP command handler or the user application code.
A HIGH level after reset on pin P2_7, starts the boot process either from on-chip flash if
available or from an external boot source for flashless parts depending on the
configuration of the OTP memory or the boot pins (see
).
A LOW level after reset on pin P2_7 indicates an external hardware request to start the
ISP command handler:
•
On parts with on-chip flash, the setting of the OTP bits and the boot pins determine
which USART (USART0 or USART3) is configured for ISP communication (see
•
On flashless parts, ISP communication uses USART0 regardless of the settings of the
OTP bits or the boot pins.
When the ISP mode is entered after a power-on-reset, the IRC and PLL1 are used to
generate the core clock of 96 MHz. Pins P2_0 and P2_1 are used for communication with
the USART0 and pins P2_3 and P2_4 are used for USART3. The UART PCLK (from
BASE_UART0/3_CLK) is set to the IRC (12 MHz).
After determining the host’s baud rate, the test string “Synchronized” is sent to a host.
After a successful handshake, ISP enters the command interpret mode.
Table 29.
ISP functionality for flash parts
ISP pin P2_7
Flash image
Action
HIGH
Valid flash image
Boot from flash.
HIGH
Invalid flash
image
Check OTP for ISP source pins (USART0 or USART3) If
OTP BOOT_SRC = 0x0, check boot pins. See
.
LOW
-
Check OTP for ISP mode or external boot. If OTP
BOOT_SRC = 0x0 and boot pins are all LOW, enter ISP
mode via USART0.See
.
Table 30.
ISP functionality for flash-less parts
ISP pin P2_7
Action
HIGH
Boot from external source as indicated by OTP or boot pins. See
LOW
Enter ISP mode using USART0, pins P2_0 and P2_1