ATECC508A datasheet(44/109 Pages) MICROCHIP

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6.5

I2C Transmission from the ATECC508A

When the ATECC508A is awake and not busy, the bus master can retrieve the current buffer contents

from the device using an I2C Read. If valid command results are available, the size of the group returned

is determined by the particular command which has been run (see Section Security Commands);

otherwise, the size of the group (and the first byte returned) will always be four: count, status/error, and 2-

byte CRC. The bus timing is shown in Figure 8-3.

Table 6-3. I2C Transmission from the ATECC508A

Name

I2C Name

Direction Description

Device

Address

Device

Address

To slave

This byte selects a particular device on the I2C interface and ATECC508A

will be selected if bits 1 through 7 of this byte match bits 1 thru 7 of the

I2C_Address byte in the Configuration zone. Bit 0 of this byte is the

standard I2C R/W pin, and should be one to indicate that the bytes following

the device address travel from the slave to the master (Read).

Data

Data1,N

To master The output group, consisting of the count, status/error byte or the output

packet followed by the two byte CRC per Section I/O Groups.

The status, error, or command outputs can be read repeatedly by the master. Each time a Read

command is sent to the ATECC508A along the I2C interface, the device transmits the next sequential

byte in the output buffer. See the following section for details on how the device handles the address

counter.

If the ATECC508A is busy, idle, or asleep, it will NOT ACK the device address on a read sequence. If a

partial command has been sent to the device and a read sequence [Start + DeviceAddress(R/W

== R)] is sent to the device, then the ATECC508A will not ACK the device address to indicate that no

data is available to be read.

6.6

Address Counter

Writes to and/or reads from the ATECC508A I/O Buffer over the I2C interface are treated as if the device

were a FIFO. Either the I2C byte or page write/read protocols can be used. The number of bytes

transferred with each page sequence does not affect the operation of the device.

The first byte transmitted to the device is treated as the size byte. Any attempt to send more than this

number of bytes, or any attempts to write beyond the end of the I/O Buffer (71 bytes) will cause the

ATECC508A to not ACK those bytes.

After the host writes a single command byte to the input buffer, reads are prohibited until after the device

completes command execution. Attempts to read from the device prior to the last command byte being

sent will result in an ACK of the device address but all ones (0xFF) on the bus during the data intervals

because the device is still waiting for the completion of the command transmission. If the host attempts to

send a read byte after the last byte of the command has been transmitted, the device will be executing

the command and will NOT ACK the device address.

Data may be read from the device under the following three conditions:

•

On power-up, the single byte 0x11 (Section Status/Error Codes) can be read inside a four byte

group.

•

If a complete block has been received by the device, but there are any errors in parsing or

executing the command, a single byte of error code is available (also inside a four byte group).

ATECC508A

I2C Interface

Datasheet Complete

DS20005927A-page 44

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