FS5600 : NOT Registers

[BENSA123]

Hello NXP , 
according to the FS5600 datasheet , it states that for registers that contain secure bits , it is obligatory to write to the register itself and its respective NOT register . 
When interfacing with an MFS5600AMBA0ES , we remarked that a write to just the register (without any writes to the NOT register) is enough and the content of the register is overwritten .

Is this behaviour normal ? I thought the NOT logic registers are available for all ASILB parts .

Best Regards

[guoweisun]

Hi 

You'd better operate the respective NOT register also.

Hope this could help you!

Thanks!

[BENSA123]

I don't really get what you mean .
In my case the register's value changes even when i don't modify the NOT register . 
Is this normal behaviour ? is there some usecase where NOT registers are disabled for example through an OTP register etc ...

Br

[guoweisun]

1:In my case the register's value changes even when i don't modify the NOT register . 
Is this normal behaviour ? is there some usecase where NOT registers are disabled for example through an OTP register etc ...

[gw]That's normal behavior but we don't recommend you do that, you'd better operate this NOT register also.

[guoweisun]

1:In my case the register's value changes even when i don't modify the NOT register . 
Is this normal behaviour ? is there some usecase where NOT registers are disabled for example through an OTP register etc ...

[gw]That's normal behavior but we don't recommend you do that, you'd better operate this NOT register also.

[BENSA123]

Could you please share with me what could potentially happen if NOT registers are also not modified . 
Just for some general reference ! 

Thanks in advance for the help ! 

[guoweisun · Accepted solution]

I confirmed in the EVB:

That behavior CAN NOT change SBC configuration at last even though you can Write it successful, if no operate the related NOT register.

So you need operate the register and related NOT register together for getting successfully.

[guoweisun]

That behavior should not change SBC configuration at last even though you can Write it successful., if no operate the related NOT register.

I will confirm again in the EVB tomorrow and let you know the result.

[BENSA123]

>"That behavior should not change SBC configuration at last even though you can Write it successful"
Do you confirm that the value of the Register is indeed modified BUT the written configuration will not be taken into consideration ?
For Example : 
FS5600_WriteRegister(Reg,dummy) ---> val = FS5600_ReadRegister(Reg) , should i expect val to be equal to dummy but the dummy configuration will not affect the Sbc functionality unless we also write to the NOT register ?

Is my assumption correct ?
Thank you in advance 

[guoweisun]

It can be simply understood that you first write to the relevant registers without writing to the NOT registers. Therefore, the registers updated first will not have any effect on the SBC. The SBC will only be updated when the NOT registers are changed accordingly.