Rainbow Electronics DS2778 - Manual (Page 37)

DS2775/DS2776/DS2777/DS2778
2-Cell, Stand-Alone, Li+ Fuel-Gauge IC with
Protector and Optional SHA-1 Authentication
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register, address 1Fh, bit 6) to a 1. If the LOCK bit is 0
or if setting the LOCK bit to 1 does not immediately
precede the Lock command, the Lock command has no effect. The Lock command is permanent; a locked
block can never be written again.
COMMAND HEX DESCRIPTION
Write Challenge 0Ch
Writes 64-bit challenge for SHA-1 processing. Required immediately prior
to all Compute MAC and Compute Next Secret commands.
Compute MAC without ROM ID (and
Return MAC for the DS2776 only)
36h
Computes hash of the message block with logical 1s in place of ROM ID.
(Returns the 160-bit MAC for the DS2776 only.)
Compute MAC with ROM ID (and Return
MAC for the DS2776 only)
35h
Computes hash of the message block using the ROM ID. (Returns the
160-bit MAC for the DS2776 only.)
Clear Secret 5Ah Clears the 64-bit secret to 0000 0000 0000 0000h.
Compute Next Secret without the ROM ID 30h Generates new global secret.
Compute Next Secret with ROM ID 33h Generates new unique secret.
Read ROM ID (DS2778 only) 39h Returns the ROM ID (DS2778 only).
Read MAC (DS2778 only) 3Ah Returns the 160-bit MAC (DS2778 only).
Lock Secret 60h Sets lock bit to prevent changes to the secret.
Read Data 69h, XXh Reads data from memory starting at address XXh.
Write Data 6Ch, XXh Writes data to memory starting at address XXh.
Copy Data 48h, XXh Copies shadow RAM data to EEPROM block containing address XXh.
Recall Data B8h, XXh Recalls EEPROM block containing address XXh to RAM.
Lock 6Ah, XXh Permanently locks the block of EEPROM containing address XXh.
Reset BBh Resets DS2775/DS2776 (software POR).
Table 12. All Function Commands
COMMAND
ISSUE MEMORY ADDRESS
(BITS)
ISSUE 00h BEFORE READ READ/WRITE TIME SLOTS
Write Challenge — — Write: 64
Compute MAC — Yes Read: Up to 160
Compute Next Secret — — —
Clear/Lock Secret, Set/Clear — — —
Read Data 8 — Read: Up to 2048
Write Data 8 — Write: Up to 2048
Copy Data 8 — —
Recall Data 8 — —
Lock 8 — —
Reset — — —
Table 13. Guide to Function Command Requirements