LP-AM243: AM243x: Understanding SBL_null

Tai-Phan Vuong

Part Number: LP-AM243

Hello TI-Support Team,

I have got some questions about the SBL_x, especially SBL_null.

Due to the descriptions for the examples, the "Flash SOC Initialization Binary" with downloading of SBL_null into flash shall be done once before going on with the examples.

1. What is it really for ? Is it a prerequisite for debugging SW via JTAG interface ?

2. It shall be done once because there is no access to MCU via JTAG interface possible ?

3. Access to MCU via JTAG is there any prerequisites ?

I would like to understand it clearly since on our target hardware there will be NO any serial interfaces, the boot mode will be set fixed to OSPI/QSPI Flash via resistors, only the JTAG interface will be provided. So there is only one way to download the SBL into the flash => via JTAG interface.

Thanks in advance for your reply and clarification.

over 3 years ago

+1 Frank Livingston over 3 years ago

TI__Mastermind 29868 points

Hi Tai-Phan,

Tai-Phan Vuong said:
What is it really for ?

SBL NULL is used for SOC initialization. Please see https://software-dl.ti.com/mcu-plus-sdk/esd/AM243X/08_02_00_31/exports/docs/api_guide_am243x/EXAMPLES_DRIVERS_SBL_NULL.html

Tai-Phan Vuong said:
Is it a prerequisite for debugging SW via JTAG interface ?

No, JTAG can be used to debug SW with any SOC initialization method. The different SOC initialization methods are described here:

Tai-Phan Vuong said:
It shall be done once because there is no access to MCU via JTAG interface possible ?

No, the OSPI flash only needs to be programmed with SBL NULL once. Thereafter, the SOC will be initialized from flash in OSPI boot mode. CCS/JTAG can still be used to the any core.

Obviously SBL NULL would need to be programmed to the OPSI flash again if:

the flash is erased and written with some other program
there is a desire to update the SBL NULL version, e.g. with a new release of the SDK.

Tai-Phan Vuong said:
Access to MCU via JTAG is there any prerequisites ?

No, just follow the instructions here: https://software-dl.ti.com/mcu-plus-sdk/esd/AM243X/08_02_00_31/exports/docs/api_guide_am243x/CCS_SETUP_PAGE.html#autotoc_md20

For SBL NULL, the R5F0_0 GEL file isn't needed. This GEL file can be replaced with the GEL file associated with the other R5F cores.
In the CCS target configuration, select R5F0_0 and replace "..\..\emulation\gel\AM24x\AM24_DDRSS\AM24x_GP_EVM.gel" with "..\..\emulation\gel\AM24x\CPU_reset.gel".

Regards,
Frank

0 Tai-Phan Vuong over 3 years ago in reply to Frank Livingston

Prodigy 40 points

Hi Frank,

much thanks for your clarification.

So if the JTAG interface is always accessible even if the out-the-box flash device is not yet initilalized, so the SBL_null or SBL_ospi could be flashed via JTAG interface. Usually there are some 3rd party tools which provide scripts for flashing via JTAG interface.

So it is not required to provide any serial interface e. g. UART on target hardware.

Can you confirm ?

Thanks,

Tai-Phan

+1 Frank Livingston over 3 years ago in reply to Tai-Phan Vuong

TI__Mastermind 29868 points

Hi Tai-Phan,

A JTAG-based flashing tool will be available in the upcoming 08.03.00 release. The scheduled release date is end of May.

Regards,
Frank

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LP-AM243: AM243x: Understanding SBL_null