at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 43

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Boot Program
Overview
1790A–ATARM–11/03
The Boot Program downloads an application in any of the AT91 products integrating a ROM. It
integrates a Bootloader and a boot Uploader to assure correct information download.
The Bootloader is activated first. It looks for a sequence of eight valid ARM exception vectors
in a DataFlash connected to the SPI, an EEPROM connected to the Two-wire Interface (TWI)
or an 8-bit memory device connected to the external bus interface (EBI) (if the device inte-
grates the EBI). All these vectors must be B-branch or LDR load register instructions except
for the sixth instruction. This vector is used to store information, such as the size of the image
to download and the type of DataFlash device.
If a valid sequence is found, code is downloaded into the internal SRAM. This is followed by a
remap and a jump to the first address of the SRAM.
If no valid ARM vector sequence is found, the boot Uploader is started. It initializes the Debug
Unit serial port (DBGU) and the USB Device Port. It then waits for any transaction and down-
loads a piece of code into the internal SRAM via a Device Firmware Upgrade (DFU) protocol
for USB and XMODEM protocol for the DBGU. After the end of the download, it branches to
the application entry point at the first address of the SRAM.
The main features of the Boot Program are:
•
•
•
•
•
•
•
•
Default Boot Program stored in ROM-based products
Downloads and runs an application from external storage media into internal SRAM
Downloaded code size depends on embedded SRAM size
Automatic detection of valid application
Bootloader supporting a wide range of non-volatile memories
–
–
–
Boot Uploader in case no valid program is detected in external NVM and supporting
several communication media
Serial communication on a DBGU (XModem protocol)
USB Device Port (DFU Protocol)
SPI DataFlash
Two-wire EEPROM
8-bit parallel memories on NCS0 (only for devices with EBI integrated)
®
connected on SPI NPCS0
AT91RM3400
43