SLVSJC6 December 2025 TPS544B27W
PRODUCTION DATA
PASSKEY is shown in Figure 7-4 and described in Table 7-5.
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Write Transaction: Block Write
Read Transaction: Block Read
Data Format: Writes Unsigned Binary (4 bytes); Reads Unsigned Binary (3 bytes)
NVM Back-up: EEPROM
Updates: On-the-fly. STORE_USER_ALL then power on reset required for the PASSKEY to be locked. The PMBus 1.5 standard command PASSKEY provides a customer with the ability to lock access to (C7h) EXTENDED_WRITE_PROTECT with a user programmed up to 32-bit passkey. PASSKEY will accept fewer or more bytes on a write without NACKing or an invalid data response. Writing a non-zero value using PASSKEY will lock write access to EXT_WRITE_PROTECT only after sending a STORE_USER_ALL command and performing a power on reset, or sending a RESTORE_USER_ALL command. In any PASSKEY state the user can read a total of 3 bytes from PASSKEY, with the 2 additional bytes being a user option reporting a NVM_CHECKSUM value based on the contents of the non-volatile memory. Data Validity: Writes between 2 and 8 bytes will be acknowledged. Any other number of bytes are considered as invalid data. Additionally when the PASSKEY is set but unlocked, writes to PASSKEY other than all bytes 00h or the current PASSKEY are considered as invalid data. In both cases the device responds as described in the IVD bit in STATUS_CML.
| 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 |
| NVM_CHECKSUM[15:0] | |||||||
| R-0h | |||||||
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| NVM_CHECKSUM[15:0] | |||||||
| R-0h | |||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| RESERVED | RESERVED | RESERVED | PASSKEY_LOCK | PASSKEY_ATTEMPTS[3:0] | |||
| R-0h | R-0h | R-0h | R-0h | R-0h | |||
| Bit | Field | Type | Reset | Description |
|---|---|---|---|---|
| 23:8 | NVM_CHECKSUM[15:0] | R | 0h | NVM_CHECKSUM reports the CRC-16 (polynomial 0x8005) checksum for the current NVM settings. The PASSKEY NVM bits are excluded from the checksum to prevent a malicious actor from reading the device configuration and repeatedly setting PASSKEY values in an attempt to discover the PASSKEY value. |
| 7 | RESERVED | R | 0h | |
| 6 | RESERVED | R | 0h | |
| 5 | RESERVED | R | 0h | |
| 4 | PASSKEY_LOCK | R | 0h | This bit reflects the lock status if the PASSKEY.
|
| 3:0 | PASSKEY_ATTEMPTS[3:0] | R | 0h | This bit returns the number of invalid PASSKEY write attempts to unlock PASSKEY. After 3 invalid attempts a power on reset is required for further attempts.
|