Sam AV3 stops working

[lodesmets]

Hello,

In our design we are planning to use the SAM AV3. 

The processor we are using is a Microchip SAME54

Our startup procedure is as follows:

- unplug our device

- insert sam card

- plug in device

- enable voltage on the sam card

- pull-up the io line

- enable the clock

- pull high the reset line

Then we get an ATR.

If we pull out the power on our board and plug it in again, the card is dead.

We can't find any reason. We noticed we had a 100 ohm resistor on the data line, this one we already swapped for a 1K

[Florian_Mikulik]

Hello @lodesmets,

Usually, those cards are resistant to removing without powering off/deactivating properly, so i do not see an issue there. But, if you speak of powering off the whole board, I could imagine that some voltage levels on the board may act unwanted/undefined, leading to a "parasitic powering" of the SAM AV3 through e.g. IO1, which in turn can lead a security shutdown of the SAM AV3. This state is permanent, and can not be reversed.

What I would like to ask for is (if possible) and oscilloscope picture of VCC, IO1 and CLK and RST at the SIM socket when you pull the power from the board. What we would like to see is, that VCC is always the highest voltage present on the SAM AV3. If this is not the case (i've seen that on some MCU's already) then possibly increasing C53 could help.

Do you have any pullups on IO1, CLK or RST?

Thanks,

Florian

[lodesmets]

Hello,

Do you have any pullups on IO1, CLK or RST?

Yes, and no. we have pull-ups, but they are software defined in the chip.

I have added the screenshots of the signals when VCC is removed. (named VCC_"the other pin I'm measuring".png. The blue line is always VCC)

None of the voltages go above VCC. But they all go down together.

I have done some more tests with the "Contact Deactivation Sequence". And if we shutdown the card, and then remove VCC, the card keeps working. So that is great.

But that would also mean that for the safety of the card, we need to shutdown the card when it is idle in case VCC gets removed. Our application is an access control controller, so technically the power should never be removed. But it is still important that if the power is removed (power loss, maintenance of the power supply/ backup battery, ...) that we don't break any sam cards.

which in turn can lead a security shutdown of the SAM AV3

I'm guessing you aren't allowed to tell us a lot about the tamper detection/ security shutdown?

But is it something that is timed? If it detects 2 bad shutdowns in 1hour it goes into security shutdown. But if the bad shutdowns are days appart everything is fine?

Thanks,

Lode

[lodesmets]

I forgot to upload the attachment

[Florian_Mikulik]

Hi @lodesmets,

Unfortunately I can not discuss security related information via the pubic community, but we can follow up via email if you want to!

regarding your problem: The pictures look good, so actually I would not expect any problems from this. The voltage on VCC is falling very slowly though, can you confirm that it reaches 0V until you power up again? Maybe the problem lies not in the power down, but the next power up starting from an undefined condition? You could try to remove/short L54 and C53, to ensure VCC reaches 0V, to check if this is the reason.

best regards,

Florian

[Kan_Li]

Hi @lodesmets ,

What do you mean for the power on your board? The VCC of K50? 

You also mentioned "the card is dead" , do you mean the card can not work any more?

Please kindly clarify.

Thanks for your patience!

Have a great day,
Kan

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[lodesmets]

Hello,

With unplugging and plugging the board in, I mean enabling (and disabling) VDD. This is also the power source to the CPU (SAME54)

We have an usb smart card reader (ACR38) where we can test the cards. And when I say "the card is dead", I meant that the card doesn't even give an ATR when in the usb reader

I understand that smart cards have a deactivation sequence. But the problem is that our board (VDD) can switch off at any moment without us having any warning in advance. Is this the possible culprit?