DS2703 Dallas Semiconductor, DS2703 Datasheet - Page 8

• Manufacturer Part Number: DS2703
• Description: SHA-1 Battery Pack Authentication IC
• Manufacturer: Dallas Semiconductor

Table 3. Authentication Function Commands
Write Challenge
Compute MAC without ROM ID
and return MAC
Compute MAC with ROM ID and
return MAC
SECRET MANAGEMENT FUNCTION COMMANDS
LOAD SECRET [5Ah]. This command writes the 64-bit secret to the provided 64-bit data argument value. The host
must apply a programming pulse to write the secret value to EEPROM.
COMPUTE NEXT SECRET WITHOUT ROM ID [30h]. This command initiates a SHA-1 computation of the MAC
and uses a portion of the resulting MAC as the next or new secret. The MAC computation is performed with the
current 64-bit secret and the 64-bit challenge. Logical 1’s are loaded in in place of the ROM ID since the ROM ID
data is not used in this command. Two words (64 bits) of the output MAC are used as the new secret value. The
host must allow t
pulse to write the new secret value to EEPROM.
COMPUTE NEXT SECRET WITH ROM ID [33h]. This command initiates a SHA-1 computation of the MAC and
uses a portion of the resulting MAC as the next or new secret. The MAC computation is performed with the current
64-bit secret, the 64-bit ROM ID, and the 64-bit challenge. Two words (64 bits) of the output MAC are used as the
new secret value. The host must allow t
apply a programming pulse to write the new secret value to EEPROM.
LOCK SECRET [6Ah]. This command write protects the 64-bit Secret to prevent accidental or malicious overwrite
of the secret value. The Secret value stored in EEPROM becomes "final." The host must apply a programming
pulse to write the secret lock bit to EEPROM.
Table 4. Secret Loading Function Commands
Load Secret
Compute Next Secret without
ROM ID
Compute Next Secret with
ROM ID
Lock Secret
1-Wire SPEED CONTROL FUNCTION COMMANDS
CLEAR OVERDRIVE [8Dh]. This command clears the 1-Wire Overdrive bit to select the Standard 1-Wire timings
shown in the Electrical Characteristics table. The Overdrive bit is stored in EEPROM so that the programmed
speed selection can be recalled on initial power up. The host must apply a programming pulse to complete the
command.
SET OVERDRIVE [8Bh]. This command sets the 1-Wire Overdrive bit to select the Overdrive 1-Wire timings
shown in the Electrical Characteristics table. The Overdrive bit is stored in EEPROM so that the programmed
speed selection can be recalled on initial power up. The host must apply a programming pulse to complete the
command.
COMMAND
COMMAND
COMP
after issuing this command for the SHA calculation to complete, then apply a programming
HEX
5A
6A
30
33
HEX
0C
36
35
COMP
Loads the Secret with 64-bit data argument
Generates new global secret
Generates new unique secret
Sets lock bit to prevent changes to the Secret
Writes 64-bit challenge for SHA-1 processing. Required prior to
either Compute MAC command.
Computes hash with logical 1’s in place of the ROM_ID
Computes hash including the ROM_ID
after issuing this command for the SHA calculation to complete, then
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FUNCTION
FUNCTION