6.1 Counter Command

The Counter command reads or increments the binary count value from the monotonic counter located on the device within the Configuration zone. The maximum value of the counter is fixed at 10,000. The starting value of the counter is programmed during initial provisioning and, when CSZ2 is locked, it cannot be modified.

The counter is designed to never lose counts even if the power is interrupted during the counting operation. In some power loss conditions, the counter may increment by a value of more than one.

The counter can be attached to the secret key in Slot 3 to limit its use. The counter will be incremented whenever the MAC command is called or until the counter has reached its maximum value, at which point, use of the key will no longer be permitted and an execution error will occur.

The number of legal uses for a key can also be controlled by initializing the counter to a non-zero value at configuration time. Contact Microchip for details.