ATECC508A datasheet(47/109 Pages) MICROCHIP

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General Purpose I/O Pin

When the Single-Wire Interface is enabled, the SCL pin is available to be used as a GPIO pin. It may be

used to drive one or two LEDs or can be connected to an external tamper detection switch or connected

in many other ways. When configured as an output, it may be used as an enable pin for some external

component in the system which may require cryptographic validation prior to assertion.

On initial power-up, the pin is always temporarily configured as an input. During the device initialization,

which occurs with the very first wake operation, the contents of the I2C_Address field are read and the

GPIO pin will be driven to the state. The direction (input or output) and state (if an output) of the GPIO pin

will remain unchanged during sleep and idle states. The actions of this pin are controlled by the

I2C_Address byte in the Configuration zone, and the GPIO mode of the Info command as described in

the table below:

Table 7-1. GPIO Mode

Bit 3 Bit 2 Bit 1 Bit 0 Name

Power-

Up State

Meaning

Disable

Input

The SCL pin is unused and should be tied to GND. Any attempt to

execute the GPIO mode of the Info command will result in an error

code being returned to the system firmware. The GPIO mode of the

Info command will also return an error code if the part is configured

for I2C operation.

Auth0

Low

The SCL pin will be permanently configured as an output and will be

driven to a zero (default) state when the first wake operation after

power-up occurs. The pin can then be driven to the opposite ('1')

state by the Info command if a prior authorization has been

performed using the SignalKey slot. The GPIO output mode of the

Info command can be used to reset the pin back to the default

value without authorization. The GPIO retains its state so long as

VCC remains above 2V.

Auth1

High

As Auth0; however, the default state after power-up is one.

Intrusion

Input

The SCL pin will be permanently configured as an input. On power-

up, an internal intrusion latch is set to zero. The intrusion latch is set

via authorization and is cleared if SCL falls. The state of latch can

be determined via the Info command. It will remain in that state so

long as a voltage greater than 1.8V is applied to the SCL pin and

VCC remains above 2.0V regardless of the internal state (asleep,

idle, or wake) of the ATECC508A. Any falling edge on the SCL pin

resets the intrusion latch to zero regardless of whether or not the

ATECC508A is in wake or sleep mode. Reading the state of the

GPIO pin via the Info command returns the value of the intrusion

latch; not the current state of the pin.

Input

The SCL pin will remain permanently configured as an input.

Execution of the Info command will permit the current state on the

pin to be returned to the system firmware.

Output0

Low

The SCL pin will be configured as an output and will be driven to a

zero state when the first wake operation occurs. Subsequent Info

commands can be executed to drive the pin high or low.

ATECC508A

General Purpose I/O Pin

Datasheet Complete

DS20005927A-page 47

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