Secure Manager: ITS storage size configuration

[jjm]

Hi,

we have a question regarding the Secure Manager Internal Trusted Storage size on the STM32H73 series.
We have configured the following options:

• external flash profile
• 0 secure modules (=SMAK_0 ?)

According to UM3254 it is our understanding the ITS size can now be up to 56 Kbyte:

Our application project.py prebuild seems to extract value “9”, which means 9 * 8 Kbyte (Flash sector size) = 72 Kbyte?

 

Jul  8 13:27:10 2026 : [INF] Searching the parameter with <Name>ITS size</Name> element
2026-07-08 13:27:10,542 - DEBUG - Wed Jul  8 13:27:10 2026 : [INF] Parameter found. Verifying information of '<Value>0x9</Value>'
2026-07-08 13:27:10,543 - DEBUG - Wed Jul  8 13:27:10 2026 : [INF] The modification is not necessary
2026-07-08 13:27:10,543 - DEBUG - Wed Jul  8 13:27:10 2026 : [INF] The tag <Value> has already the correct content (0x9)

 

Is there a misunderstanding on our end about the profile, memory configuration, UM3254 table, the prebuild proccess or the conversion factor between the prebuild factor 0x09 and Kbyte?

Because 0x09 * 4 Kbyte would fit the 36Kbyte user data size from the table above. 
However “ITS Factory size” is extracted as 0x02, and that expresses 2 * 8 Kbyte = 16 Kbyte according to documentation.

Thank you and best regards
Jakob

[Jocelyn RICARD]

Hello ​@jjm ,

This size of 9 sectors provided in the xml configuration file (C:\ST\X-CUBE-SEC-M-H5_V2.1.0\Projects\STM32H573I-DK\ROT_Provisioning\SM\Config\Profile_External_Flash\SM_Config_General_Ext_Flash.xml) also includes the 2 sectors used by the Factory ITS (see paragraph 4.1.3.3) .

So, 7*8KB = 56KB for dynamic ITS + 2*8KB = 16KB of factory ITS.

The second column actually shows maximum available size for user. The ITS requires some spare sectors to manage robust updates.

Best regards

Jocelyn

[jjm]

Thank you, that resolves my confusion!