ATSHA204 datasheet(36/65 Pages) ATMEL

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Atmel ATSHA204 [DATASHEET]

8740D

−CRYPTO−3/12

8.1.5

Zone Encoding

The value in Param1 controls which zone the command accesses. See Section 2.1.2.1, “Configuration Zone Locking,” to

obtain more information on what controls the “locked” and “unlocked” states for each zone. All other zone values are reserved,

and should not be used.

Table 8-8.

Zone Encoding (Param1)

Zone

Name

Param1

Value

Size

Read

Write

Config

512 bits,

64 bytes,

2 slots

Always available

Partially, when unlocked

Never when locked

Never encrypted

OTP

512 bits,

64 bytes,

2 slots

Never when unlocked. Always

when locked, except in legacy

mode. See Section 2.1.3

All writeable when unlocked using Write

When locked, write permissions depend on OTPmode

See Section 2.1.3

Data

4096 bits,

512 bytes,

16 slots

Never when unlocked.

Otherwise, controlled by

IsSecret and EncryptRead.

All writeable when unlocked

When locked, writes controlled by WriteConfig

8.1.6

Watchdog Failsafe

A watchdog counter starts within the device after the ATSHA204 receives a wake token. After tWATCHDOG, the device enters

sleep mode, regardless of whether some I/O transmission or command execution is in progress. There is no way to reset the

counter other than to put the device into sleep or idle mode and then wake it up again.

The watchdog timer is implemented as a failsafe mechanism so that no matter what happens on either the system side or

inside the device, including any I/O synchronization issue, power consumption will fall to the ultra-low sleep level automatically.

The device resets the values stored in the SRAM and internal status registers when it transitions to the sleep state. However, if

the device is explicitly put into the idle mode through the appropriate I/O sequence, the device retains the contents of the two

SRAM registers (TempKey and RNG seed).

Normally, all command sequences must complete within tWATCHDOG if they require state that is stored in the SRAM registers.

The system software can use this idle mode mechanism to implement a longer command sequence than can be completed

during a single watchdog interval.

ATSHA204 Datasheet(PDF) 36 Page - ATMEL Corporation

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