SLVSH95 July 2024 TPS546C25
ADVANCE INFORMATION
| CMD Address | 0Eh |
| Write Transaction: | Write Block (4 Bytes) |
| Read Transaction: | Read (3 Bytes) |
| Format: | Unsigned Binary (4 bytes or 3 bytes) |
| Phased: | Yes |
| NVM Back-up: | EEPROM |
| Updates: | On-the-fly |
The PMBus 1.5 standard command PASSKEY provides a customer with the ability to lock access to EXT_WRITE_PROTECTION with a User Programmed up to 32-bit passkey[KJ1] . The PASSKEY will accept fewer or more bytes on a write without NACKing.
Return to Supported PMBus Commands.
| 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 |
| R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W |
| PASSKEY_3 | PASSKEY_2 | ||||||
| 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W |
| PASSKEY_1 | PASSKEY_0 | ||||||
| LEGEND: R/W = Read/Write; R = Read only |
Writing a non-zero value using PASSKEY will lock write access to EXT_WRITE_PROTECT (and STORE_USER_ALL if SNVML (EXT_WP[0]) is set) only after sending a STORE_USER_ALL command and performing a POWER_ON_RESET, or sending the PMBus command RESTORE_USER_ALL.
As a user option the NVM_CHECKSUM is read back as the next two bytes after the PASSKEY data.
When PASSKEY = 0000h, EXT_WRITE_PROTECT is unlocked and writable unless write protected by WRITE_PROTECT or EXT_WRITE_PROTECT . Non-Volatile memory is Unlocked. STORE commands function normally unless write protected by WRITE_PROTECT or EXT_WRITE_PROTECT . A READ on PASSKEY that has not yet been written will return 0000h. A WRITE on PASSKEY will set PASSKEY to be stored to NVM via STORE_USER_ALL.
When PASSKEY =! 0000h, Non-Volatile memory is locked. STORE_USER_ALL and EXT_WRITE_PROTECT is NACKED as “UNSUPPORTED or INVALID DATA”
A READ on PASSKEY will report a value of:
If a WRITE on PASSKEY does not match the value of PASSKEY in PASSKEY at Power On Reset or RESTORE_USER_ALL, the PASSKEY invalid access attempt counter is incremented. If the Counter reaches 3, all further WRITE attempts are considered invalid and the device will NACK and set IVD_DATA bit in STATUS_CML
If the WRITE data matches the Passkey used to PASSKEY access and less than 3 invalid attempts have been made, PASSKEY is allowed to be overwritten with a new PASSKEY value, including 0000h and the Invalid Attempts counter is reset to 0.