ATECC508A datasheet(43/109 Pages) MICROCHIP

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Table 6-2. Word Address Values

Name

Value

Description

Reset

0x00

Reset the address counter. The next I2C read or write transaction will start with the

beginning of the I/O buffer.

Sleep

(Low-power)

0x01

The ATECC508A goes into the low power sleep mode and ignores all subsequent I/O

transitions until the next wake flag. The entire volatile state of the device is reset.

Idle

0x02

The ATECC508A goes into the idle mode and ignores all subsequent I/O transitions

until the next wake flag. The contents of TempKey and RNG Seed registers are

retained.

Command

0x03

Write subsequent bytes to sequential addresses in the input command buffer that

follow previous writes. This is the normal operation.

Reserved

0x04 –

0xFF

These addresses should not be sent to the device.

6.2.2

Command Completion Polling

After a complete command has been sent to the ATECC508A, the device will be busy until the command

computation completes. The system has two options for this delay as noted below:

•

Polling:

The system should wait tEXEC (typical) and then send a read sequence (see Section I2C

Transmission from the ATECC508A). If the device NOT ACKs the device address, then it is still

busy. The system may delay for some time or immediately send another read sequence, again

looping on NOT ACK. After a total delay of tEXEC (max), the device will have completed the

computation and return the results.

•

Single Delay:

The system should wait tEXEC (max) after which the device will have completed execution, and the

result can be read from the device using a normal read sequence.

6.3

Sleep Sequence

Upon completion of the use of the ATECC508A by the system, the system should issue a sleep sequence

to put the device into low power mode. This sequence consists of the proper device address followed by

the value of 0x01 as the word address 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.

6.4

Idle Sequence

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

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

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

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

The 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.

ATECC508A

I2C Interface

Datasheet Complete

DS20005927A-page 43

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