ATECC508A datasheet(42/109 Pages) MICROCHIP

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6.2

I2C Transmission to ATECC508A

The transmission of data from the system to the ATECC508A is summarized in the table below. The order

of transmission is as follows:

•

Start Condition

•

Device Address Byte

•

Word Address Byte

•

Optional Data Bytes (1 through N)

•

Stop Condition

Figure 6-4. Normal I2C Transmission to ATECC508A

1-7

SCL

SDA

R/W

ACK1

Word

Address

Data 1

ACK1

Data 2

Start

Condition

Stop

Condition

Device

Address

ACK1

Data N

SDA is driven low by ATECC508A ACK periods.

The tables below label the bytes of the I/O transaction. The column labeled “I2C Name” provides the

name of the byte as described in the AT24C16 data sheet.

Table 6-1. I2C Transmission to ATECC508A

Name

I2C Name

Description

Device

Address

Device

Address

This byte selects a particular device on the I2C interface. ATECC508A is selected if

the data shifted out on clock pulses 1-7 match the data stored in the I2C_Address

byte in the Configuration zone. Data is shifted out MSb first. Bit 0 of this byte (clock

pulse 8) is the standard I2C R/W bit, and should be zero to indicate a write operation

(the bytes following the device address travel from the master to the slave).

Word Address Word

Address

This byte should have a value of 0x03 for normal operation. See Sections Word

Address Values and Address Counter for more information.

Command

Data1,N

The command group, consisting of the count, command packet, and the two byte

CRC. The CRC is calculated over the size and packet bytes. See Section I/O

Groups.

Because the device treats the command input buffer as a FIFO, the input group can be sent to the device

in one or many I2C command groups. The first byte sent to the device is the count, so after the device

receives that number of bytes, it will ignore any subsequently received bytes until execution is finished.

The system must send a Stop condition after the last command byte to ensure that ATECC508A will start

the computation of the command. Failure to send a Stop condition may eventually result in a loss of

synchronization; see Section I2C Synchronization for recovery procedures.

6.2.1

Word Address Values

During an I2C write packet, the ATECC508A interprets the second byte sent as the word address, which

indicates the packet function as it is described in the table below:

ATECC508A

I2C Interface

Datasheet Complete

DS20005927A-page 42

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