MAX34446
PMBus Power-Supply Data Logger
any reason more than the expected number of bytes or
bits is written to the device, the device does the following:
1) Ignores the command.
2) Sets the CML bit in STATUS_BYTE.
3) Sets the CML bit in STATUS_WORD.
4) Sets the DATA_FAULT bit in STATUS_CML.
Host Reads Too Many Bytes or Bits
For each supported command, the device expects a fixed
number of bytes to be read from the device. If for any
reason more than the expected number of bytes or bits is
read from the device, the device does the following:
1) Sends all ones (FFh) as long as the host keeps
acknowledging.
2) Sets the CML bit in STATUS_BYTE.
3) Sets the CML bit in STATUS_WORD.
4) Sets the DATA_FAULT bit in STATUS_CML.
Host Sends Improperly Set Read Bit
in the Slave Address Byte
If the device receives the R/ W bit in the slave address set
to one immediately preceding the command code, the
device does the following:
1) ACKs the address byte.
2) Sends all ones (FFh) as long as the host keeps
acknowledging.
3) Sets the CML bit in STATUS_BYTE.
4) Sets the CML bit in STATUS_WORD.
5) Sets the DATA_FAULT bit in STATUS_CML.
Unsupported Command Code Received
If the host sends the device a command code that it does
not support, or if the host sends a command code that
is not supported by the current PAGE setting, the device
does the following:
1) Ignores the command.
2) Sets the CML bit in STATUS_BYTE.
3) Sets the CML bit in STATUS_WORD.
4) Sets the COMM_FAULT bit in STATUS_CML.
Invalid Data Received
The device checks the PAGE and WRITE_PROTECT
command codes for valid data. If the host writes a data
value that is invalid, the device does the following:
1) Ignores the command.
Maxim Integrated
2) Sets the CML bit in STATUS_BYTE.
3) Sets the CML bit in STATUS_WORD.
4) Sets the DATA_FAULT bit in STATUS_CML.
Host Reads from a Write-Only Command
When a read request is issued to a write-only com-
mand (CLEAR_FAULTS, STORE_DEFAULT_ALL, and
RESTORE_DEFAULT_ALL), the device does the following:
1) ACKs the address byte.
2) Ignores the command.
3) Sends all ones (FFh) as long as the host keeps
acknowledging.
4) Sets the CML bit in STATUS_BYTE.
5) Sets the CML bit in STATUS_WORD.
6) Sets the DATA_FAULT bit in STATUS_CML.
Host Writes to a Read-Only Command
When a write request is issued to a read-only command,
the device does the following:
1) Ignores the command.
2) Sets the CML bit in STATUS_BYTE.
3) Sets the CML bit in STATUS_WORD.
4) Sets the COMM_FAULT bit in STATUS_CML.
SMBus Timeout
If during an active SMBus communication sequence
the SCL signal is held low for greater than the timeout
duration (t TO ), the device terminates the sequence and
resets the serial bus. It takes no other action. No status
bits are set.
PMBus Operation
From a software perspective, the device appears as a
PMBus device capable of executing a subset of PMBus
commands. A PMBus 1.1-compliant device uses the
SMBus version 1.1 for transport protocol and responds
to the SMBus slave address. In this data sheet, the term
SMBus is used to refer to the electrical characteristics
of the PMBus communication using the SMBus physical
layer. The term PMBus is used to refer to the PMBus com-
mand protocol. The device employs a number of stan-
dard SMBus protocols to program voltage warning/faults
thresholds, read monitored data, and provide access to
all manufacturer-specific commands.
The device supports the group command. The group
command is used to send commands to more than one
PMBus device. It is not required that all the devices
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