Functional Description
The ROM Code uses the row pointed by the SYSBOOT pins value. The device list is filled in with the 1
st
to
4
th
devices.
is the decoding table for SYSBOOT pin configuration. The following shortcuts are used in the
table:
•
MMC1: MMC or SD card (MMC port 1)
•
MMC0: MMC or SD card (MMC port 0)
•
NAND / NANDI2C: NAND flash memory / read geometry from EEPROM on I2C0
•
XIP: NOR or other XIP device without wait monitoring
•
XIP w/ WAIT: NOR or other XIP device with wait monitoring
•
MUX1: Boot with XIP_MUX1 signals detailed in
•
MUX2: Boot with XIP_MUX2 signals detailed in
•
UART0: UART interface (UART port 0)
•
EMAC1: Ethernet interface (EMAC port 1)
•
SPI0: SPI EEPROM (SPI 0, CS0)
•
USB0: USB interface (USB0)
Note: For any SYSBOOT value that is selected, please be aware of the pin muxing implications. For
example, if the boot mode selected is EMAC1, NAND, SPI0, NANDI2C, the device will drive EMAC,
GPMC, SPI and I2C pins, in that order, depending on which boot device finally succeeds. Ensure that if a
specific boot mode in the sequence chosen is not used that the components using those particular signals
do not conflict with the ROM driving those signals (or external components are not in contention with the
ROM using these signals). For specific details of the pins driven by each device, please refer the
description of that boot device later in this chapter.
To extend the boot flow to boot from devices that are not natively supported by the ROM, SPI boot can be
used. For example, to be able to boot from a USB stick, the system can be configured to boot from a SPI
flash, and the code for configuring the USB and booting from a USB stick can be loaded into the SPI
flash. This is known as a secondary boot.
The values corresponding to SYSBOOT[4:0]= x1111 provide a bypass mode booting feature.
The fast external boot feature consists of minimal execution by the ROM Code for configuring the GPMC
interface and then directly jump to the code contained in the connected NOR flash device.
26.1.6 Fast External Booting
26.1.6.1 Overview
The Fast External boot feature:
•
Consists of a blind jump in ARM mode to address 0x08000000 in an external XIP device connected to
CS0
•
The jump is performed with minimum on-chip ROM Code execution (only configures GPMC interface),
without configuring any PLL
•
Allows the customer to create its own booting code
•
Is set up by means of the configuration pins, see
•
Addr/Data muxed device or a non-muxed (selected using SYSBOOT[11:10]) device in connected in
XIP_MUX1 configuration
•
Bus width selected by SYSBOOT[8]
•
CS0 chip select
•
No wait monitoring is available
26.1.6.2 External Booting
shows the Fast External Boot procedure. The code does not make use of RAM and is
designed for fast execution.
4112
Initialization
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated