CryptoCompanion™ Chip
5
5277DS–CryptoCompanion–9/09
The system processor is expected to properly format commands for CryptoCompanion (which may include information
from the CRF chip), and then process the outputs of CryptoCompanion (which may include sending some of the
outputs to the CRF chip).
CryptoCompanion cannot directly communicate with CRF chips. Both CRF and CryptoCompanion 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.
1.4. Memory Locking
When this initialization is complete the Lock command should be executed which limits access to the memory per the
restrictions listed later in this section. The system can determine the current lock value by using the
ReadManufacturingID command to read out the ManufacturingID value (MfrID) and the lock byte.
The table below describes the encoding of the least significant two bits of the Lock byte. On shipment from Atmel,
Lock[1:0] will have a value of either 10 or 00, depending on the part number ordered. An AT88SC018 in either of these
two states is considered ‘unlocked’. It is not possible to change from one of these unlocked states to the other.
After the Lock command has been executed, the Lock byte will have the value 0xFF. Subsequent changes to the Lock
byte are impossible.
Table 2. Memory Locking
LockBit 1 Lock Bit 0 (LSB) Meaning
1 1 Locked. ReadMemory & WriteMemory enabled, subject to the restrictions in this
section. WriteMemoryEncrypted and ReadMemoryDigest disabled.
1 0 Unlocked/Confidential. ReadMemoryDigest, WriteMemory and
WriteMemoryEncrypted enabled. ReadMemory disabled.
0 0 Unlocked. ReadMemory & WriteMemory enabled. WriteMemoryEncrypted and
ReadMemoryDigest disabled.
2. AC & DC Characteristics
Table 3. DC Characteristics
(1)
Applicable over recommended operating range from V
CC
= +2.7 to 3.6 V,
T
AC
= -40
o
C to 85
o
C (unless otherwise noted)
Symbol Parameter Test Condition Min Typ Max Units
V
CC
Supply Voltage 2.7 3.6 V
I
CC
Supply Current 400kHz 5 mA
I
SB
Standby Current V
IN
= V
CC
or GND 15 μA
V
IL
SDA Input Low Voltage -0.3 V
CC
x 0.3 V
V
IL
CLK Input Low Voltage -0.3 V
CC
x 0.3 V
V
IL
RST Input Low Voltage -0.3 V
CC
x 0.3 V
V
IL
PDN Input Low Voltage -0.3 V
CC
x 0.3 V
V
IH
SDA Input High Voltage V
CC
x 0.7 5.25 V
V
IH
SCL Input High Voltage V
CC
x 0.7 5.25 V
V
IH
RST Input High Voltage V
CC
x 0.7 5.25 V
