DS2778 Maxim Integrated Products, DS2778 Datasheet - Page 33

• Manufacturer Part Number: DS2778
• Description: 2-Cell Stand-Alone Li+ Fuel-Gauge IC
• Manufacturer: Maxim Integrated Products

Table 9. Memory Map (continued)
Each DS2775–DS2778 has a unique, factory-pro-
grammed ROM ID that is 64 bits. The first 8 bits of the
net address are the product family code (32h). The next
48 bits are a unique serial number. The last 8 bits are a
cyclic redundancy check (CRC) of the first 56 bits (see
Figure 22).
The DS2776/DS2778 have an authentication feature
that is performed using a FIPS 180-compliant SHA-1
one-way hash algorithm on a 512-bit message block.
The message block consists of a 64-bit secret, a 64-bit
Figure 22. 1-Wire Net Address Format (ROM ID)
* Register value is automatically saved to EEPROM during active-mode operation and recalled from EEPROM on power-up.
Protector and Optional SHA-1 Authentication
ADDRESS (HEX)
B2h to FDh
81h to AFh
64-Bit Net Address (ROM ID)
20h to 2Fh
30h to 5Fh
60h to 80h
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
1Ah
1Bh
1Ch
1Dh
B0h
B1h
13h
14h
15h
16h
17h
18h
19h
1Eh
1Fh
FEh
FFh
______________________________________________________________________________________
MSb
8-BIT CRC
Accumulated Current Register LSB - 2
Age Scalar Register
Special Feature Register
Full Register MSB
Full Register LSB
Active-Empty Register MSB
Active-Empty Register LSB
Standby-Empty Register MSB
Standby-Empty Register LSB
Voltage Register MSB, V
Voltage Register LSB, V
Cycle Counter Register
EEPROM Register
User EEPROM Register, Lockable, Block 0
Reserved
Parameter EEPROM Register, Lockable, Block 1
Reserved
Factory Gain RSGAIN Register MSB
Factory Gain RSGAIN Register LSB
Reserved
2-Wire Command Register
Reserved
Authentication
48-BIT SERIAL NUMBER
DESCRIPTION
IN2
IN2
- V
- V
IN1
IN1
challenge, and 384 bits of constant data. Optionally,
the 64-bit net address replaces 64 of the 384 bits of
constant data used in the hash operation. Contact
Maxim for details of the message block organization.
The host and the DS2776/DS2778 both calculate the
result based on the mutually known secret. The result
data, known as the message authentication code
(MAC) or message digest, is returned by the
DS2776/DS2778 for comparison to the host’s result.
Note that the secret is never transmitted on the bus and
thus cannot be captured by observing bus traffic. Each
authentication attempt is initiated by the host system by
providing a 64-bit random challenge through the Write
8-BIT FAMILY
CODE (32h)
LSb
READ/WRITE
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R/W*
R/W*
R/W
R/W
R/W
R/W
—
—
—
—
W
R
R
R
R
R
R
R
R
R
R
R
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