How to program stm32L552 using SWD interface

[angry.sioux]

I use my own application to program different devices, arm in particular. Now, i'd like to support stm32L552. So, if TZEN = 0 it works fine.

if TZEN = 1, DBANK = 1, SECWM1_PSTRT - set as secure, SECWM2_PSTRT - set as non-secure, RDP = 0xaa (level 0) i cant read flash using SWD. STM32CubeProgrammer works perfectly in both cases.

I'd appreciate any help

[Imen.D]

Hello @angry.sioux​ and welcome to the Community :)

Check if the SWD is mapped on the right pin.

I advise you to refer to this article: Security:How to disable TrustZone in STM32L5xx devices during development phase

Imen

[angry.sioux]

Hi Imen,

>>Check if the SWD is mapped on the right pin.

I cannot read only the FLASH in case of TZEN = 1. But I read registers (CTRL_STAT, IDR...), can read OPTR, FLASHSIZE_BASE and so on. So, it;s not about a SWD pin.

>>I advise you to refer ....

I have read  Security:How to disable TrustZone in STM32L5xx devices during development phase and did not find an answer. Otherwise I would never reach out to for a favor.

Thank you

[angry.sioux]

I found a way that made things a bit better.

There is WAIT response if i access to AP register. But.

If i read a register twice the error goes away.

f.e. schematically

//do not need to read, just write

write_register ( SELECT_REG, bank select for CSW_REG)

write_register ( SELECT_REG, bank select for TAR_REG) - error, WAIT

but

write_register ( SELECT_REG, bank select for CSW_REG)

read_reg(CSW_REG) - dummy read, enough for "no error", but returns trash.

read_reg(CSW_REG) - returns appropriate value

write_register ( SELECT_REG, bank select for TAR_REG) - no error, great

but

if i halt and reset core i got DHCSR_S_LOCKUP

[angry.sioux]

Thanks for the quick reply and detailed answers to all inquiries. Thank you so much.

To simplify the process i'll split the problem into small pieces.

To write a some array i need to specify address (TAR) and tell CSW that i want to CSW_SIZE_32BITS, CSW_ADDRINC. After that i can write DRW in the loop as much as I need to. That is always how it has worked.

Now (in stm32L552 ) i see that i need to add dummy read after each iteration. Otherwise, i'm getting WAIT response.

The one question. Why?

[angry.sioux]

You have been very helpful. Thank you. Thanks to your help i found out a workaround by adding idle request after writing. Though I still don't understand the difference with previous devices.

But now i faced with next problem. I halt the core and change PC (some code in this address). After start the core i get LOCKUP. (PC not 0xfffffffe) I do what used to do with numerous previous devices. I hope you'll help me in this case as you did it before. I have read you comments with great interest and pleasure. It's a pity that SWD pins on the right place.

Thank you so much.