ATSHA204 datasheet(33/65 Pages) ATMEL

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Atmel ATSHA204 [DATASHEET]

8740D

−CRYPTO−3/12

8.1.2

Status/Error Codes

The device does not have a dedicated status register, and so the output FIFO is shared among status, error, and command

results. All output from the device is returned to the system as complete blocks, which are formatted identically to input blocks:

• Count

• Packet

• 2-byte CRC

After the device receives the first byte of an input command block, the system cannot read anything from the device until the

system has sent all the bytes to the device.

After wake and after execution of a command, there will be error, status, or result bytes in the device’s output register that can

be retrieved by the system. When the length of that block is four bytes, the codes returned are detailed below in Table 8-3.

Some commands return more than four bytes when they execute successfully: the resulting packet description is listed in the

command section below.

CRC errors are always returned before any other type of error. They indicate that some sort of I/O error occurred and that the

command may be resent to the device. If a command includes both parse and execution errors, there is no particular

precedence enforced – an execution error may occur before a parse error and/or the reverse.

Table 8-3.

Status/error Codes in 4-byte Blocks

State Description

Error/Status

Description

Successful

Command Execution

0x00

Command executed successfully.

Checkmac

Miscompare

0x01

The CheckMac command was properly sent to the device, but the input client

response did not match the expected value.

Parse Error

0x03

Command was properly received, but the length, command opcode, or parameters

are illegal, regardless of the state (volatile and/or EEPROM configuration) of the

ATSHA204.

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, but prior

to first command

0x11

Indication that the ATSHA204 has received a proper wake token.

CRC or other

Communications

Error

0xFF

Command was not properly received by the ATSHA204, and should be

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

No attempt was made to parse or execute the command.

ATSHA204 Datasheet(PDF) 33 Page - ATMEL Corporation

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