DS2704 Maxim Integrated Products, DS2704 Datasheet - Page 6

• Manufacturer Part Number: DS2704
• Description: 1280-Bit EEPROM
• Manufacturer: Maxim Integrated Products

Table 1. Authentication Function Commands
COMMAND
Write Challenge
Compute MAC without ROM ID
and return MAC
Compute MAC with ROM ID and
return MAC
SECRET MANAGEMENT FUNCTION COMMANDS
CLEAR SECRET [5Ah]. This command sets the 64-bit secret to all 0’s (0000 0000 0000 0000h). The host must
wait t
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 place of the ROM ID. 64-bits of the output
MAC are used as the new secret value. The host must allow t
calculation to complete, then wait t
page 17 for command timing.
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. 64-bits of the output MAC are used as the new secret
value. The host must allow t
the DS2704 to write the new secret value to EEPROM. See Figure 8 on page 17 for command timing.
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 wait t
to write the lock secret bit to EEPROM. See Figure 10 on page 18 for command timing.
Table 2. Secret Loading Function Commands
COMMAND
Clear 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 selects the Standard 1-Wire timings shown in the Electrical
Characteristics table. The setting is stored in EEPROM so that the programmed speed selection can be recalled on
initial power up. The host must wait t
Standard 1-Wire timing is the factory default.
SET OVERDRIVE [8Bh]. This command selects the Overdrive 1-Wire timings shown in the Electrical
Characteristics table. The setting is stored in EEPROM so that the programmed speed selection can be recalled on
initial power up. The host must wait t
EEC
for the DS2704 to write the new secret value to EEPROM. See Figure 10 on page 18 for command timing.
SHA
after issuing this command for the SHA calculation to complete, then wait t
EEC
Hex
5A
6A
30
33
EEC
EEC
Hex
0C
36
35
for the DS2704 to write the new secret value to EEPROM. See Figure 8 on
for the DS2704 to write the EEPROM. See Figure 10 for command timing.
for the DS2704 to write the EEPROM. See Figure 10 for command timing.
FUNCTION
Clears the 64-bit Secret to 0000 0000 0000 0000h
Generates new global secret
Generates new unique secret
Sets lock bit to prevent changes to the Secret
FUNCTION
Writes 64-bit challenge for SHA-1 processing. Required prior to
issuing Compute MAC and Compute Next Secret commands.
Computes hash the message block with logical 1’s in place of the
ROM ID. Returns the 160-bit MAC.
Computes hash of the message block including the ROM ID.
Returns the 160-bit MAC.
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SHA
after issuing this command for the SHA
EEC
for the DS2704
EEC
for