at88sc018 ATMEL Corporation, at88sc018 Datasheet - Page 5

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

1.4.4. Environmental
1.4.5. TWI Input/Output Operation
5277C–CryptoCompanion–9/09
The AT88SC018 is guaranteed to operate over the industrial temperature range of -40°to 85°C. ESD is rated at 2KV,
Human Body Model.
The AT88SC018 communicates to the system using a two wire interface (TWI), which is similar to SMBus™. The chip
operates as a slave and does not support clock stretching. This two wire protocol is identical to that supported by the
Atmel AT24C16B serial EEPROM chips. Refer to the datasheet on the Atmel web site for detailed timing and protocol
information.
The system processor is expected to properly format commands for the AT88SC018 (which may include information
from the CRF chip), and then process the outputs of the AT88SC018 (which may include sending some of the outputs
to the CRF chip).
The AT88SC018 cannot directly communicate with CRF or CM chips. Both CRF/CM and the AT88SC018 are slave
devices. The bus master may use one or two busses to communicate with them. Separate TWI addresses must be
used if both chips are on the same bus.
Table 2.
If the upper 6 bits of the device address byte sent over the TWI match the upper 6 bits of the Dev field in the EEPROM,
then the AT88SC018 may respond to this transmission, otherwise it will NACK this byte. Dev is set to a value of 0xC0
on shipment from Atmel.
In general, the AT88SC018 will fail to ACK (NACK) the device address byte if bit 1 of the device address is 0
(command/data transfer) and the AT88SC018 is busy.
The AT88SC018 is designed in such a way that the TWI Size field should be consistent with the count values specified
in the command parameter descriptions from
command parameter count value, the AT88SC018 will respond in different ways depending on the specific command.
Some of these responses may include security penalties, other error indications or some input bytes may be silently
ignored.
Device Address
Cmd
Size
Data
AT88SC018
Name
AT88SC018 communications packets naming conventions.
Device Name
Word Address
Data
Data
TWI Name
N
N+1
, …
This byte selects a particular chip on the two wire bus. Bit 1 of this byte on the
AT88SC018 selects between accesses to command/data (if 0) or the status
register (if 1). Bit 0 of this byte is the standard two wire R/W pin, if 1 then the bytes
following the device address travel from the slave to the master (Read) if 0 these
bytes flow to the slave (Write).
If the device address specified a command input (TWI write), then this byte
specifies the command to be executed by the AT88SC018. This byte doesn’t exist
on read operations.
The total number of bytes to follow this byte may be 0 in the case that there are no
operand bytes. This byte doesn’t exist on status read operations.
Operand input or output bytes as specified in the command descriptions in
Command Descriptions.
Command
Descriptions. If the TWI size field is inconsistent with the
Description
CryptoCompanion Chip
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