Use of pin 6 in IMP-001

Hi,
As per documentation, "Pin 6 is reserved for the ID chip and may not be used for any other purpose."
Could you please elaborate what exactly it means ?

Thanks
Dheeraj

This means it’s used to talk to the ATSHA chip on the host board, and you can’t use it as I/O.

Hi Hugo,
“ATSHA chip on the host board” here what is ATSHA chip and host board ?

I have below understanding please verify if it is correct.

ATSHA chip: While Micro SD card shaped while electric IMP chip.
host board: April board.

Thanks
Dheeraj

In order to run the correct firmware (squirrel), the imp needs to know which device it’s in. For imp001 cards, where you can use the same card in multiple devices, we use an external ID chip. This is the “ATSHA” chip. It’s on the host board (the April board or the Hannah board, for example), and we require that pin 6 from the imp (i.e. from the slot) is connected to it. That means you can’t use pin 6 for I/O.

Great that explains pin 6 use in lucid manner.
Thanks.