LPC55S69: RAM reservation for ROM API operations

[EugeneHiihtaja]

Hi !

I try to understand what exact RAM areas can be reserved when some ROM API called and MCU is not in ISP mode.

For example when FLASH memory API  in use or Power Management ( backup area is documented .)

1.

In UM chapter 7.3.6.6 Secure ROM API :

The ROM reserved space for global variables in RAM on this
LPC55S6x/LPC55S2x/LPC552x product is:
0x30000000 to 0x30003FFF
0x14005000 to 0x140059FF

So this is valid for Secure ROM API in case if the used or it is valid for any ROM API usage ?

2. ROM in ISP mode 

UM 8.3.4.2 RAM used by the ISP command handler

So this is for ISP mode only.

But I can't find SRAM areas what used by FLASH API.

Do you have information about it ?

Regards,

Eugene

[Sabina_Bruce]

Hello Eugene, 

1.

In UM chapter 7.3.6.6 Secure ROM API :

So this is valid for Secure ROM API in case if the used or it is valid for any ROM API usage ?

In theory you are able to use the space for any use. However if you plan on using the ROM API it is not recommended to use this space for anything other than its original purpose. If you do decide to use it for another purpose, please refer to the statement in the same section.

The caller has to assure that it doesn't have any data in the global variables location before the function call. The caller shall discard the data in the global variables location after the function returns.

2. The information is not specified.

Best Regards,

Sabina

[EugeneHiihtaja]

Hi sabinabruce‌ !

So no idea for this topic:

But I can't find SRAM areas what used by FLASH API.

Do you have information about it ?

Regards,

Eugene

[Sabina_Bruce]

Hello Eugene,

I have requested this information from our design team. I will update you as soon as I have an answer.

Regards,

Sabina

[EugeneHiihtaja]

Hi sabinabruce‌ !

Thank you !

I hope it is not so massive reservation as mentioned in 8.3.4.2 RAM used by the ISP command handler UM chapter.

Regards,

Eugene

[Sabina_Bruce]

Hello Eugene, 

I received a response from our team. 

The Flash API in LPC55S6x won't need extra RAM for Stack. Only Secure ROM API need such RAM for stack purpose.

Best Regards,

Sabina

[EugeneHiihtaja]

Hi Sabina !

Thank you !

It means POWER API is not used "external" SRAM as well. Is this so ?

Regards,

Eugene

[Sabina_Bruce]

 If CPU retention used in power-down mode, SRAMX_2 (0x1400 6000 to 0x1400 65FF) is used (total 1.5 KB) by default in Power API.