MCU-PLUS-SDK-AM263X: ROM Bootloader behavior and OSPI

Hi DeviPrasad,

Deviprasad Nagadavalli said:

As per reference manual section 5.2.1.1 Public ROM Entry, ROM bootloader performs clearing core registers, PBIST on TCMB, setting of of main stack, TI auto init and then branches to main code.

1. Can we get access to the source code or related details to these tasks in ROM bootloader? 

No ROM code is confidential as it holds details related to device integrity, so it is not shared.

Deviprasad Nagadavalli said:

• What is TI auto init?
• What is the meaning of branch to main? Is it referring to main code of ROM bootloader or main code of SBL?

It refers to SBL code, you will not see the sysmbols of ROM code, symbols of SBLs/application are only visible

Deviprasad Nagadavalli said:

If we want to use Execute in Place (XIP) feature to execute the code directly from external flash then does SBL needs any specific section to be initialized to handle this? 

Yes. SInce SBL is responsible for loading the application image to individual cores, in case of XIP, SBL sets up the OSPI peripheral in DAC(DIrect Access mode) for enabling XIP.

Deviprasad Nagadavalli said:

Can SBL be executed directly in external flash in XIP mode? 

No, SBL cannot be executed from flash, it needs to be run from RAM.

How application code present in flash memory be executed in XIP mode? Will the application code be copied in buffer memory to execute the code or Does it execute the code directly from flash?

Shitanshu Desai said:

• What is the typical time taken by the ROM bootloader to transfer control to the secondary bootloader?
• In Dev boot code(debug build), how should memory be defined in the linker file for the secondary bootloader? Would ROM bootloader code be executed in debug mode?

For RBL boottime:  [FAQ] AM2634: MCU-PLUS-SDK-AM263X: How to understand/optimize the boot time of RBL/SBL ? 

In DEV boot mode, ROM bootloader does very minimal configuration, and allows the application code or SBL to be loaded via jtag into RAM.

Could you explain. more what you are trying to do?

Hi Nilabh,

Thanks for your responses.

We are using AM263P microcontroller for one of the program and we need some details about RBL and plan accordingly in SBL by understanding the execution time, RBL behavior, error scenarios and failure actions. Currently my team is developing SBL and it helps us a lot if you can share more info related to our queries.

I have following open questions,

1. What is the maximum size available for the application image in L2 memory? Is there any restrictions on the number of application images and its size?
2. As per section 5.7.7 R5 SBL Handoff, HSM copies 640 bytes from the address 0x70002000 to TCMA start address 0x20000. These 640 bytes
   consists of IVT and initialization code. As per this step, what is initialization code - 640 bytes?
3. RBL perform TI auto Init as per section 5.2.1.1 Public ROM Entry. What exactly TI auto init performs in RBL?
4. As per the below link that you have shared with us, why there is a memory overlap between SBL image and application image? [FAQ] AM2634: MCU-PLUS-SDK-AM263X: How to understand/optimize the boot time of RBL/SBL ? 

Deviprasad Nagadavalli said:

What is the maximum size available for the application image in L2 memory? Is there any restrictions on the number of application images and its size?

You can use complete OCRAM for your application, one exception is the SBL overlap memory as you mentioned, which can be reclaimed later as bss memory region, once SBL has executed completed and application starts execution.

Deviprasad Nagadavalli said:

As per section 5.7.7 R5 SBL Handoff, HSM copies 640 bytes from the address 0x70002000 to TCMA start address 0x20000. These 640 bytes
consists of IVT and initialization code. As per this step, what is initialization code - 640 bytes?

IVT refers to interrupt vector table, you can refer to this file for exact IVT table contents:

mcu_plus_sdk_am263px/source/kernel/nortos/dpl/r5/HwiP_armv7r_vectors_nortos_asm.S

Deviprasad Nagadavalli said:

RBL perform TI auto Init as per section 5.2.1.1 Public ROM Entry. What exactly TI auto init performs in RBL?

Please refer to this: https://software-dl.ti.com/codegen/docs/tiarmclang/compiler_tools_user_guide/compiler_manual/runtime_environment/system-initialization-stdz0543503.html

Also for exact initialization sequence for R5F you can findit  here in the file: mcu_plus_sdk_am263px/source/kernel/nortos/dpl/r5/boot_armv7r_asm.S