2.2 Bootloader Features
This section describes in detail the boot mode selection process, as well as the specifics of the bootloader
operation.
2.2.1 Bootloader Functional Operation
The bootloader uses the state of TRST and two GPIO signals to determine which boot mode to use. The boot
mode selection process and the specifics of each bootloader are described in the remainder of this document.
shows the basic bootloader flow.
Reset
(Power-On Reset or
Warm Reset)
Silicon Sets the Following:
PIE Disabled (ENPIE=0)
VMAP=1
OBJMODE=0
AMODE=0
M0M1MAP=1
Boot ROM
Reset Vector Fetched
from Boot ROM Address
0x3F FFC0
Jump to InitBoot Function
to Start Boot Process
Call Device_cal()
PLLSTS[DIVSEL]=3
Dummy Read of CSM
Password Locations
TRST=1?
Yes
No
Debug Probe Not Connected
Determine Boot Mode
Based on 2 GPIO pins
and 2 OTP locations
(OTP_KEY and
OTP_BMODE)
Debug Probe Connected
Determine Boot Mode
Based on 2 RAM
Locations
(EMU_KEY and
EMU_BMODE)
Begin Execution at Entry
Point as Determined by
Selected Boot Modes
Figure 2-4. Bootloader Flow Diagram
The reset vector in boot ROM redirects program execution to the InitBoot function. After performing device
initialization the bootloader will check the state of the TRST pin to determine if a debugger is connected.
•
Debugger Boot (Debugger is connected and TRST = 1)
In debugger boot, the boot ROM checks two SARAM locations called EMU_KEY and EMU_BMODE for a boot
mode. If the contents of either location are invalid, then the "wait" boot mode is used. All boot mode options can
be accessed by modifying the value of EMU_BMODE through the debugger when performing a debugger boot.
Stand-alone Boot (TRST = 0)
If the device is in stand-alone boot mode, then the state of two GPIO pins are used to determine which boot
mode execute. Options include: GetMode, wait, SCI, and parallel I/O. Each of the modes is described in detail in
. The GetMode option by default boots to flash but can be customized by programming two values into
OTP to select another boot loader.
These boot modes mentioned here are discussed in detail in
After the selection process and if the required boot loading is complete, the processor will continue execution at
an entry point determined by the boot mode selected. If a bootloader was called, then the input stream loaded
by the peripheral determines this entry address. This data stream is described in
choose to boot directly to Flash, OTP, or SARAM, the entry address is predefined for each of these memory
blocks.
Boot ROM
202
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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