Datasheet

LTC2978A
33
2978afa
For more information www.linear.com/LTC2978A
WRITE_PROTECT
The WRITE_PROTECT command provides protection against accidental programming of the LTC2978A command
registers. All supported commands may have their parameters read, regardless of the WRITE_PROTECT setting.
There are two levels of write protection:
• Level 1: Nothing can be changed except the level of write protection itself. Values can be read from all pages. This
setting can be stored to EEPROM.
• Level 2: Nothing can be changed except for the level of protection, channel on/off state and clearing of faults. Values
can be read from all pages. This setting can be stored to EEPROM.
WRITE_PROTECT Data Contents
BITS(S) SYMBOL OPERATION
b[7:0] Write_protect[7:0] Level 1: 1000_0000b: Disable all writes except to the WRITE_PROTECT, PAGE, and STORE_USER_ALL commands.
Level 2: 0100_0000b: Disable all writes except to the WRITE_PROTECT, PAGE, STORE_USER_ALL, OPERATION, MFR_
PAGE_FF_MASK, and CLEAR_FAULTS.
0000_0000b: Enable writes to all commands.
xxxx_xxxxb: All other values reserved.
STORE_USER_ALL and RESTORE_USER_ALL
STORE_USER_ALL, RESTORE_USER_ALL commands provide access to User EEPROM space. Once a command is
stored in User EEPROM, it will be restored with an explicit restore command or when the part emerges from power-
on reset after power is applied. While either of these commands is being processed, the device will NACK I
2
C writes.
STORE_USER_ALL. Issuing this command will store all operating memory commands with a corresponding EEPROM
memory location. It is recommended that this command not be executed while a unit is enabled since all monitoring
is suspended while the operating memory is transferred to EEPROM.
RESTORE_USER_ALL. Issuing this command will restore all commands from EEPROM Memory. It is recommended
that this command not be executed while a unit is enabled since all monitoring is suspended
while the EEPROM is
transferred to operating memory, and intermediate values from EEPROM may not be compatible with the values initially
stored in operating memory.
CAPABILITY
The CAPABILITY command provides a way for a host system to determine some key capabilities of the LTC2978A.
This one byte command is read only.
CAPABILITY Data Contents
BITS(S) SYMBOL OPERATION
b[7] Capability_pec Hard coded to 1 indicating Packet Error Checking is supported. Reading the Mfr_config_all_pec_en bit will indicate
whether PEC is currently required.
b[6] Capability_scl_max Hard coded to 1 indicating the maximum supported bus speed is 400kHz.
b[5] Capability_smb_alert Hard coded to 1 indicating this device does have an ALERTB pin and does support the SMBus Alert Response
Protocol.
b[4:0] Reserved Always returns 0.
PMBus COMMAND DESCRIPTION