ATSHA204 ATMEL [ATMEL Corporation], ATSHA204 Datasheet - Page 24

• Manufacturer Part Number: ATSHA204
• Description: Atmel CryptoAuthentication
• Manufacturer: ATMEL [ATMEL Corporation]

6.2.1
6.2.2
6.3
6.4
Word Address Values
During an I
function, as described in the following table.
Table 6-2.
Command Completion Polling
After a complete command has been sent to the ATSHA204, the device will be busy until the command computation
completes. The system has two options for this delay:
Sleep Sequence
Upon completion of system use of the ATSHA204, 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 internal command engine and
input/output buffer. It can be sent to the device at any time when it is awake and not busy.
Idle Sequence
If the total sequence of required commands exceeds t
information stored in the volatile registers. This action can be prevented by putting the device into the idle state 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.
If TempKey was created as a result of the copy mode of the CheckMac command, it will not be retained when the part goes
into an idle state.
Name
Reset
Sleep
(low power)
Idle
Command
Reserved
•
•
Polling
Single Delay
The system should wait t
device address, then it is still busy. The system may delay for some time or immediately send another read
sequence, again looping on NACK. After a total delay of t
and return the results.
The system should wait t
from the device using a normal read sequence.
2
C write packet, the ATSHA204 interprets the second byte sent as the word address, which indicates the packet
Word Address Values
Value
0x00
0x01
0x02
0x03
0x04 – 0xFF
EXEC
EXEC
Description
Reset the address counter. The next read or write transaction will start with the
beginning of the I/O buffer.
The Atmel ATSHA204 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.
The Atmel ATSHA204 goes into the idle state and ignores all subsequent I/O transitions
until the next Wake flag. The contents of TempKey and RNG seed registers are
retained.
Write subsequent bytes to sequential addresses in the input command buffer that follow
previous writes. This is the normal operation.
These addresses should not be sent to the device.
(typical) and then send a read sequence (See Section 6.5). If the device NACKs the
(max), after which the device will have completed execution and the result can be read
WATCHDOG
, then the device will automatically go to sleep and lose any
EXEC
(max), the device will have completed the computation
Atmel ATSHA204 [DATASHEET]
8740D−CRYPTO−3/12
24