ADP1048ARQZ-R7 datasheet(37/84 Pages) AD

37 / 84 page

Data Sheet

ADP1047/ADP1048

Rev. 0 | Page 37 of 84

DATA TRANSMISSION FAULTS

Data transmission faults occur when two communicating devices

violate the PMBus communication protocol, as specified in the

PMBus specification. See the PMBus specification for more

information about each fault condition.

Corrupted Data, PEC (Item 10.8.1)

Parity error checking. Not supported.

Sending Too Few Bits (Item 10.8.2)

Transmission is interrupted by a start or stop condition before

a complete byte (eight bits) has been sent. Not supported; any

transmitted data is ignored.

Reading Too Few Bits (Item 10.8.3)

Transmission is interrupted by a start or stop condition before

a complete byte (eight bits) has been read. Not supported; any

received data is ignored.

Host Sends or Reads Too Few Bytes (Item 10.8.4)

If a host ends a packet with a stop condition before the required

bytes are sent/received, it is assumed that the host intended to

stop the transfer. Therefore, the PMBus does not consider this

to be an error and takes no action, except to flush any remain-

ing bytes in the transmit FIFO.

Host Sends Too Many Bytes (Item 10.8.5)

If a host sends more bytes than are expected for the corres-

ponding command, the PMBus slave considers this a data

transmission fault and responds as follows:

•

NACKs all unexpected bytes as they are received

•

Flushes and ignores the received command and data

•

Sets the CML bit in the STATUS_BYTE register

Host Reads Too Many Bytes (Item 10.8.6)

If a host reads more bytes than are expected for the corres-

ponding command, the PMBus slave considers this a data

transmission fault and responds as follows:

•

Sends all 1s (0xFF) as long as the host continues to

request data

•

Sets the CML bit in the STATUS_BYTE register

Device Busy (Item 10.8.7)

The PMBus slave device is too busy to respond to a request

from the master device. Not supported.

DATA CONTENT FAULTS

Data content faults occur when data transmission is successful,

but the PMBus slave device cannot process the data that is

received from the master device.

Improperly Set Read Bit in the Address Byte (Item 10.9.1)

All PMBus commands start with a slave address with the R/W

bit cleared (set to 0), followed by the command code. If a host

starts a PMBus transaction with R/W set in the address phase

(equivalent to an I2C read), the PMBus slave considers this a

data content fault and responds as follows:

•

ACKs the address byte

•

NACKs the command and data bytes

•

Sends all 1s (0xFF) as long as the host continues to

request data

•

Sets the CML bit in the STATUS_BYTE register

Invalid or Unsupported Command Code (Item 10.9.2)

If an invalid or unsupported command code is sent to the

PMBus slave, the code is considered to be a data content fault,

and the PMBus slave responds as follows:

•

NACKs the illegal/unsupported command byte and data

bytes

•

Flushes and ignores the received command and data

•

Sets the CML bit in the STATUS_BYTE register

Reserved Bits (Item 10.9.5)

Accesses to reserved bits are not a fault. Writes to reserved bits

are ignored, and reads from reserved bits return 0.

Write to Read-Only Commands

If a host performs a write to a read-only command, the PMBus

slave considers this a data content fault and responds as follows:

•

NACKs all unexpected data bytes as they are received

•

Flushes and ignores the received command and data

•

Sets the CML bit in the STATUS_BYTE register

Note that this is the same error described in the Host Sends Too

Many Bytes (Item 10.8.5) section.

Read from Write-Only Commands

If a host performs a read from a write-only command, the

PMBus slave considers this a data content fault and responds

as follows:

•

Sends all 1s (0xFF) as long as the host continues to

request data

•

Sets the CML bit in the STATUS_BYTE register

Note that this is the same error described in the Host Reads Too

Many Bytes (Item 10.8.6) section.

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