ATSHA204 datasheet(23/65 Pages) ATMEL

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Atmel ATSHA204 [DATASHEET]

8740D

−CRYPTO−3/12

6.2

2C Transmission to the Atmel ATSHA204 Device

The transmission of data from the system to the AT88SA102S is summarized in Figure 6-4. The order of transmission is:

• Start Condition

• Device Address Byte

• Word Address Byte

• Optional Data Bytes (1 through N)

• Stop Condition

Figure 6-4.

Normal I

2C Transmission to an Atmel ATSHA204

SDA

SCL

1-7

Start

Condition

Device

Address

Word

Address

Data 2

ACK1

Stop

Condition

Data N

Data 1

R/W

Note:

SDA is driven low by the Atmel ATSHA204 during the ACK periods

The tables below label the bytes of the I/O transaction. The I

2C name column provides the names of the bytes as described in

the AT24C16B datasheet.

Table 6-1.

2C Transmission to Atmel ATSHA204

Atmel ATSHA204

2C Name

Description

Device Address

This byte selects a particular device on the I

2C interface. The Atmel ATSHA204 is

selected if bits 1-7 of this byte match bits 1-7 of the I2C_Address byte in the

configuration zone. Bit 0 of this byte is the standard I

2C 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

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

See Sections 6.2.2 and 6.6, below, for more information.

Command

Data1-n

The command block, consisting of the count, command packet, and the two-byte

CRC. The CRC is calculated over the size and packet bytes. See Section 8.1.

Because the device treats the command input buffer as a FIFO, the input block can be sent to the device in one or many I

command blocks. The first byte sent to the device is the count, and 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 the ATSHA204 will start the computation of

the command. Failure to send a stop condition may eventually result in a loss of synchronization (See Section 6.7 for recovery

procedures).

ATSHA204 Datasheet(PDF) 23 Page - ATMEL Corporation

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