TMS320F28335, TMS320F28334, TMS320F28332
TMS320F28235, TMS320F28234, TMS320F28232
www.ti.com
SPRS439I–JUNE 2007–REVISED MARCH 2011
3.2.9.1 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
SCIRXDA (GPIO28)
SCI-A
SPI-A
SCITXDA (GPIO29)
SPISIMOA (GPIO16)
SPISOMIA (GPIO17)
SPICLKA (GPIO18)
SPISTEA (GPIO19)
I2C
SDAA (GPIO32)
SCLA (GPIO33)
CAN
CANRXA (GPIO30)
CANTXA (GPIO31)
McBSP
MDXA (GPIO20)
MDRA (GPIO21)
MCLKXA (GPIO22)
MFSXA (GPIO23)
MCLKRA (GPIO7)
MFSRA (GPIO5)
3.2.10 Security
The devices support high levels of security to protect the user firmware from being reverse engineered.
The security features a 128-bit password (hardcoded for 16 wait-states), which the user programs into the
flash. One code security module (CSM) is used to protect the flash/OTP and the L0/L1/L2/L3 SARAM
blocks. The security feature prevents unauthorized users from examining the memory contents via the
JTAG port, executing code from external memory or trying to boot-load some undesirable software that
would export the secure memory contents. To enable access to the secure blocks, the user must write the
correct 128-bit KEY value, which matches the value stored in the password locations within the Flash.
In addition to the CSM, the emulation code security logic (ECSL) has been implemented to prevent
unauthorized users from stepping through secure code. Any code or data access to flash, user OTP, L0,
L1, L2, or L3 memory while the emulator is connected will trip the ECSL and break the emulation
connection. To allow emulation of secure code, while maintaining the CSM protection against secure
memory reads, the user must write the correct value into the lower 64 bits of the KEY register, which
matches the value stored in the lower 64 bits of the password locations within the flash. Note that dummy
reads of all 128 bits of the password in the flash must still be performed. If the lower 64 bits of the
password locations are all ones (unprogrammed), then the KEY value does not need to match.
When initially debugging a device with the password locations in flash programmed (i.e., secured), the
emulator takes some time to take control of the CPU. During this time, the CPU will start running and may
execute an instruction that performs an access to a protected ECSL area. If this happens, the ECSL will
trip and cause the emulator connection to be cut. Two solutions to this problem exist:
1. The first is to use the Wait-In-Reset emulation mode, which will hold the device in reset until the
emulator takes control. The emulator must support this mode for this option.
2. The second option is to use the “Branch to check boot mode” boot option. This will sit in a loop and
continuously poll the boot mode select pins. The user can select this boot mode and then exit this
mode once the emulator is connected by re-mapping the PC to another address or by changing the
boot mode selection pin to the desired boot mode.
Copyright © 2007–2011, Texas Instruments Incorporated
Functional Overview
45
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