Datasheet
TMS320F28027, TMS320F28026, TMS320F28023, TMS320F28022
TMS320F28021, TMS320F28020, TMS320F280200
www.ti.com
SPRS523J –NOVEMBER 2008–REVISED OCTOBER 2013
3.2.8 Boot ROM
The Boot ROM is factory-programmed with boot-loading software. Boot-mode signals are provided to tell
the bootloader software what boot mode to use on power up. The user can select to boot normally or to
download new software from an external connection or to select boot software that is programmed in the
internal Flash/ROM. The Boot ROM also contains standard tables, such as SIN/COS waveforms, for use
in math-related algorithms.
Table 3-6. Boot Mode Selection
MODE GPIO37/TDO GPIO34/COMP2OUT TRST MODE
3 1 1 0 GetMode
2 1 0 0 Wait (see Section 3.2.9 for description)
1 0 1 0 SCI
0 0 0 0 Parallel IO
EMU x x 1 Emulation Boot
3.2.8.1 Emulation Boot
When the emulator is connected, the GPIO37/TDO pin cannot be used for boot mode selection. In this
case, the boot ROM detects that an emulator is connected and uses the contents of two reserved SARAM
locations in the PIE vector table to determine the boot mode. If the content of either location is invalid,
then the Wait boot option is used. All boot mode options can be accessed in emulation boot.
3.2.8.2 GetMode
The default behavior of the GetMode option is to boot to flash. This behavior can be changed to another
boot option by programming two locations in the OTP. If the content of either OTP location is invalid, then
boot to flash is used. One of the following loaders can be specified: SCI, SPI, I
2
C, or OTP.
3.2.8.3 Peripheral Pins Used by the Bootloader
Table 3-7 shows which GPIO pins are used by each peripheral bootloader. Refer to the GPIO mux table
to see if these conflict with any of the peripherals you would like to use in your application.
Table 3-7. Peripheral Bootload Pins
BOOTLOADER PERIPHERAL LOADER PINS
SCI SCIRXDA (GPIO28)
SCITXDA (GPIO29)
Parallel Boot Data (GPIO[7:0])
28x Control (GPIO16)
Host Control (GPIO12)
SPI SPISIMOA (GPIO16)
SPISOMIA (GPIO17)
SPICLKA (GPIO18)
SPISTEA (GPIO19)
I
2
C SDAA (GPIO32)
(1)
SCLA (GPIO33)
(1)
(1) GPIO pins 32 and 33 may not be available on your device package. On these devices, this bootload
option is unavailable.
Copyright © 2008–2013, Texas Instruments Incorporated Functional Overview 25
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