DS2703 SHA-1 Battery Pack Authentication IC

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Table 3. Authentication Function Commands

COMMAND

HEX

FUNCTION

Write Challenge

0C

Writes 64-bit challenge for SHA-1 processing. Required prior to

either Compute MAC command.

Compute MAC without ROM ID

and return MAC

36

Computes hash with logical 1’s in place of the ROM_ID

Compute MAC with ROM ID and

return MAC

35

Computes hash including the ROM_ID

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

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

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

COMMAND

HEX

FUNCTION

Load Secret

5A

Loads the Secret with 64-bit data argument

Compute Next Secret without

ROM ID

30

Generates new global secret

Compute Next Secret with

ROM ID

33

Generates new unique secret

Lock Secret

6A

Sets lock bit to prevent changes to the 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.