Datasheet

TPS40400
www.ti.com SLUS930B –APRIL 2011– REVISED OCTOBER 2011
WRITE_PROTECT (10h)
The WRITE_PROTECT command is used to control writing to the PMBus device. The intent of this command is
to provide protection against accidental changes. This command is not intended to provide protection against
deliberate or malicious changes to the device configuration or operation. All supported command parameters
may have their parameters read, regardless of the WRITE_PROTECT settings. The contents of this register can
be stored to non-volatile memory using the STORE_DEFAULT_ALL or STORE_DEFAULT_CODE commands.
Command WRITE_PROTECT
Format Unsigned binary
Bit Position 7 6 5 4 3 2 1 0
Access r/w r/w r/w X X X X X
Function bit7 bit6 bit5 X X X X X
Default Value 0 0 0 X X X X X
bit5
Bit Value ACTION
0 Enable all writes as permitted in bit6 or bit7
Disable all writes except the WRITE_PROTECT, OPERATION and ON_OFF_CONFIG.
1
(bit6 and bit7 must be 0 to be valid data)
bit6
Bit Value ACTION
0 Enable all writes as permitted in bit5 or bit7
Disable all writes except for the WRITE_PROTECT and OPERATION commands. (bit5
1
and bit7 must be 0 to be valid data)
bit7
Bit Value ACTION
0 Enable all writes as permitted in bit5 or bit6
Disable all writes except for the WRITE_PROTECT command. (bit5 and bit6 must be 0
1
to be valid data)
In any case, only one of the three bits may be set at any one time. Attempting to set more than one bit results in
an alert being generated and the cml bit is STATUS_WORD being set.
STORE_DEFAULT_ALL (11h)
The STORE_DEFAULT_ALL command stores all of the current storable register settings in the EEPROM
memory as the new defaults on power up.
It is permissible to use this command while the device is switching. Note however that the device continues to
switch but ignores all fault conditions until the internal store process has completed.
EEPROM programming faults cause the device to NACK and set the 'cml' bit in the STATUS_BYTE and the 'oth'
bit in the STATUS_CML registers.
RESTORE_DEFAULT_ALL (12h)
The RESTORE_DEFAULT_ALL command restores all of the storable register settings from EEPROM memory.
This command should not be used while the device is actively switching. If this is done, the device stops
switching the output drivers and the output voltage drops. Depending on loading conditions, the output voltage
could reach an undervoltage level and trigger an undervoltage fault response if programmed to do so. The
command can be used while the device is switching, but it is not recommended as it results in a restart that could
disrupt power sequencing requirements in more complex systems. It is strongly recommended that the device be
stopped before issuing this command.
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