X80000 Datasheet, PDF (32/37 Pages) Intersil Corporation – Smart Power Plug Penta-Power Sequence Controller with Hot Swap

X80000, X80001
Bus Interface Information
Interface Conventions
The device supports a bidirectional bus oriented protocol.
The protocol defines any device that sends data onto the
bus as a transmitter, and the receiving device as the
receiver. The device controlling the transfer is called the
master and the device being controlled is called the slave.
The master always initiates data transfers, and provides the
clock for both transmit and receive operations. Therefore,
the devices in this family operate as slaves in all
applications.
It should be noted that the ninth clock cycle of the read
operation is not a “don’t care.” To terminate a read operation,
the master must either issue a stop condition during the
ninth cycle or hold SDA HIGH during the ninth clock cycle
and then issue a stop condition.
Serial Clock and Data
Data states on the SDA line can change only during SCL
LOW. SDA state changes during SCL HIGH are reserved for
indicating start and stop conditions (See Figure 37).
Serial Start Condition
All commands are preceded by the start condition, which is a
HIGH to LOW transition of SDA when SCL is HIGH. The
device continuously monitors the SDA and SCL lines for the
start condition and will not respond to any command until
this condition has been met.
Serial Stop Condition
All communications must be terminated by a stop condition,
which is a LOW to HIGH transition of SDA when SCL is
HIGH, followed by a HIGH to LOW transition of SCL. The
stop condition is also used to place the device into the
Standby power mode after a read sequence.
Serial Acknowledge
Acknowledge is a software convention used to indicate
successful data transfer. The transmitting device, either
master or slave, will release the bus after transmitting eight
bits. During the ninth clock cycle, the receiver will pull the
SDA line LOW to acknowledge that it received the eight bits
of data (See Figure 38).
The device will respond with an acknowledge after
recognition of a start condition and if the correct Device
Identifier and Select bits are contained in the Slave Address
Byte. If a write operation is selected, the device will respond
with an acknowledge after the receipt of each subsequent
eight bit word. The device will acknowledge all incoming data
and address bytes, except for the Slave Address Byte when
the Device Identifier and/or Select bits are incorrect.
In the read mode, the device will transmit eight bits of data,
release the SDA line, then monitor the line for an
acknowledge. If an acknowledge is detected and no stop
condition is generated by the master, the device will continue
to transmit data. The device will terminate further data
transmissions if an acknowledge is not detected. The master
must then issue a stop condition to return the device to
Standby mode and place the device into a known state.
SCL
SDA
Start
Stop
FIGURE 37. VALID START AND STOP CONDITIONS
SCL from
Master
1
Data Output from
Transmitter
8
9
Data Output from
Receiver
Start
Acknowledge
FIGURE 38. ACKNOWLEDGE RESPONSE FROM RECEIVER
Device Addressing
Addressing Protocol Overview
Depending upon the operation to be performed on each of
these individual parts, a 1, 2 or 3 Byte protocol is used. All
operations however must begin with the Slave Address Byte
being clocked into the SMBus port on the SCL and SDA
pins. The Slave address selects the part of the device to be
addressed, and specifies if a Read or Write operation is to
be performed.
Slave Address Byte
Following a START condition, the master must output a
Slave Address Byte. This byte consists of three parts:
• The Device Type Identifier which consists of the most
significant four bits of the Slave Address (SA7 - SA4). The
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FN8148.0
March 18, 2005