ATSHA204A datasheet(18/93 Pages) MICROCHIP

18 / 93 page

Name

Bit Length Description

SourceFlag

The source of the randomness in TempKey:

0 =

Internally generated random number (Rand).

1 =

Input seed only, no internal random generation (Input).

GenData

0 = TempKey.SlotID is not meaningful and is ignored.

1 =

The contents of TempKey were generated by GenDig using one of the slots in the

Data zone (and TempKey.SlotID is meaningful).

CheckFlag

0 =

TempKey contents have been generated using a Nonce, SHA or GenDig without a

CheckMac key restriction.

1 =

The contents of TempKey were generated by the GenDig command and at least

one of the keys used in that generation is restricted to the CheckMac command

(SlotConfig.CheckOnly is one)

Valid

0 =

The information in TempKey is invalid.

1 =

The information in TempKey is valid.

In this specification, the name “TempKey” refers to the contents of the 32-byte (256-bit) Data register. The

remaining bit fields are referred to as TempKey.SourceFlag, TempKey.GenData and so on.

The TempKey.Valid bit is cleared to zero under any of the following circumstances:

•

Power-up, sleep, brown-out, watchdog expiration, or tamper detection. The contents of TempKey

are however retained when the device enters idle mode.

•

After the execution of any command other than Nonce or GenDig, regardless of whether or not the

command execution succeeds. It may be cleared by the CheckMac command unless a successful

copy takes place. It is not cleared if there is a communications problem, as evidenced by a Cyclic

Redundancy Check (CRC) error.

•

An error during the parsing or execution of a GenDig and/or Nonce command.

•

Execution of GenDig replaces any previous output of the Nonce command with the output of the

GenDig command. Execution of the Nonce command likewise replaces any previous output of the

GenDig command.

ATSHA204A

Device Organization

DS40002025A-page 18

ATSHA204A Datasheet(PDF) 18 Page - Microchip Technology

ATSHA204A Datasheet(HTML) 18 Page - Microchip Technology

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