ATSHA204A datasheet(43/93 Pages) MICROCHIP

43 / 93 page

State Description

Error/

Status

Description

Changes in the value of the command bits must be made before it is

re-attempted.

Execution Error

0x0F

Command was properly received, but could not be executed by the

device in its current state.

Changes in the device state or the value of the command bits must be

made before it is re-attempted.

After Wake, Prior to First

Command

0x11

Indication that the ATSHA204A has received a proper Wake token.

CRC or other

Communications Error

0xFF

Command was not properly received by the ATSHA204A and should be

re-transmitted by the I/O driver in the system.

No attempt was made to parse or execute the command.

8.2

Sleep Sequence

Upon completion of system use of the ATSHA204A, the system should issue a sleep sequence to put the

device into low-power mode. Using the I2C interface, this sequence consists of the proper device address

followed by the sleep flag followed by a Stop condition. This transition to the low-power state causes a

complete reset of the device’s internal command engine and input/output buffer. It can be sent to the

device at any time when it is awake and not busy.

8.3

Idle Sequence

If the total sequence of required commands exceeds tWATCHDOG, then the device automatically goes to

sleep and loses any information stored in the volatile registers. This action can be prevented by putting

the device into the idle state prior to completion of the watchdog interval. When the device receives the

Wake token, it then restarts the watchdog timer and execution can be continued.

Using the I2C interface, this idle sequence consists of the proper device address followed by the value of

0x02 as the word address followed by a Stop condition. It can be sent to the device at any time when it is

awake and not busy.

If TempKey was created as a result of the copy mode of the CheckMac command, it will not be retained

when the part goes into an idle state.

8.4

Watchdog Failsafe

A watchdog counter starts within the device after the ATSHA204A 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 falls 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

ATSHA204A

Security Commands

DS40002025A-page 43

ATSHA204A Datasheet(PDF) 43 Page - Microchip Technology

ATSHA204A Datasheet(HTML) 43 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93

Datasheet Download

Link URL