at88sc018 ATMEL Corporation, at88sc018 Datasheet - Page 7

• Manufacturer Part Number: at88sc018
• Description: Cryptocompanion? Chip For Cryptomemory And Cryptorf
• Manufacturer: ATMEL Corporation

5277C–CryptoCompanion–9/09
1.4.5.2. Command Output
The command output can be extracted from the AT88SC018 using the following byte sequence.
Table 5.
Command output bytes can be repeatedly read from the AT88SC018 as they remain valid until a new command is sent
to the AT88SC018. Until <size> bytes of the new command have been sent, DataAvailable will remain set and that
number of bytes can be read from the SRAM output buffer, though the new input bytes will overwrite the old output
bytes.
Some commands do not have any data output, for instance ‘Clear’. On completion of these commands, the
DataAvailable bit will be cleared and the system can read just the size byte, which will have a value of 0.
1.4.5.3. Status
This register can be read to determine the current status or the error information using the following byte stream. This
sequence can be run at any time, regardless of whether or not the AT88SC018 is busy or locked.
Table 6.
The status register value is described in the following table:
Table 7.
The 8 error codes are used as follows:
0
1
2, …
0
1
0
1
2
3 – 4
5 – 7
Byte #
Byte #
Byte #
To Slave
To Master
To Master
To Slave
To Master
Data Available
Busy
StartupDone
Reserved
Error
Command Output Byte Sequence
Byte Stream Sequence
Status Register Value
Direction
Direction
Name
Device Address
Size
Data
Device Address
Status
The AT88SC018 has completed processing of the command and data is available in the
output buffer. A successfully completed command that does not have any output will
NOT set this bit.
The AT88SC018 is processing a command and is unable to accept more input or provide
output, or it is in some sort of security penalty period.
The ChallengeResponse command has successfully run this power cycle. Once set, this
bit will remain set until the next reset or power cycle.
Will always be 0.
An error occurred during prior input or command processing. The value of these three
bits denotes the particular condition that occurred.
Name
Name
This byte selects a particular chip on the two wire bus. Bit 1 of this byte
should be 0 to indicate that this is a command output. Bit 0 of this byte
should be 1 to indicate that the data will travel from the slave to the
master.
The total number of bytes to follow this byte may be 0 in the case that
there are no output bytes.
Output bytes as specified in
This byte selects a particular chip on the two wire bus. Bit 1 of this byte
should be 1 to select the status register. Bit 0 of this byte is the
standard two wire R/W pin and should be 1 (data bytes travel from the
slave to the master).
Returns the current value of the status register.
Description
CryptoCompanion Chip
Command Descriptions.
Description
Description
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