DSC boot ROM: can it be reprogrammed?

[Steve_AIMMS]

Is the boot ROM space available for use, or is it one-time burned at the factory?  I have my own CAN-based bootloader code that I've used on previous DSCs, and would like to do the same with the latest (56F83783).  That 32kbyte of boot ROM would be nice to use, but I can't see anything in the documentation about possible write access - the documentation talks only about program flash read/write access. Is the boot ROM available for write access or would I have to use up sectors of the program flash to house any custom boot code?

[xiangjun_rong]

Hi, Stephen,

Regarding your question, pls refer to Chapter 6 ROM Bootloader in MC56F83xxxRM.pdf, I copy it here:

From the screenshot, you can see that the boot ROM of MC56F83xxx supports uart, CAN interface.

pls refer to the Bootloader-utility-for-MC56F83xxx, it describes how to download application code to MC56F83789 via blhost tools and uart interface.

https://community.nxp.com/t5/Digital-Signal-Controllers/Bootloader-utility-for-MC56F83xxx/ta-p/11032...

Regarding the CAN interface, it is said it is okay to use blhost tools to download code via CAN bus, but I never have a test.

Hope it can help you

BR

XiangJun Rong

[Steve_AIMMS]

Thanks for the reply.  However, I would like to use my own bootloader and preferably replace the factory-installed version.  Is the boot ROM burnable somehow (via JTAG?), or is it truly ROM burned at the factory and can't be modified in any way (burned once and done)?

[xiangjun_rong · Accepted solution]

Hi, Stephen,

The Bootloader ROM is truly ROM burned at the factory and can't be modified in any way (burned once and done)，but I think you can ignore the internal ROM bootloader, and burn your own bootloader into high address flash, have the DSC enter your own Flash bootloader after Reset as you have done.

Pls refer to the section 6.3.2 Start-up Process, it tells you how to bypass the internal ROM bootloader and jump to your own flash bootloader.

"

The FOPT register determines the boot source. The FOPT register is loaded from the
flash configuration field at address 0x40D in flash memory. The value of
FOPT[7:6]&(~SIM_BOOT_MODE_OVERRIDE[BOOT_OVERRIDE]) determines the
boot option: value 11b means booting from ROM, while any other value means booting
from flash.

"

Hope it can help you

BR

XiangJun Rong