Datasheet

78M6610+PSU Data Sheet
Bus Characteristics
• A data transfer may be initiated only when the bus is not busy.
• During data transfer, the data line must remain stable whenever the clock line is HIGH. Changes in
the data line while the clock line is HIGH will be interpreted as a START or STOP condition.
Bus Conditions:
• Bus not Busy (I): Both data and clock lines are HIGH indicating an Idle Condition.
• Start Data Transfer (S): a HIGH to LOW transition of the SDA line while the clock (SCL) is HIGH
determines a START condition. All commands must be preceded by a START condition.
• Stop Data Transfer (P): a LOW to HIGH transition of the SDA line while the clock (SCL) is HIGH
determines a STOP condition. All operations must be ended with a STOP condition.
• Data Valid: The state of the data line represents valid data when, after a START condition, the data
line is stable for the duration of the HIGH period of the clock signal. The data on the line must be
changed during the LOW period of the clock signal. There is one clock pulse per bit of data. Each
data transfer is initiated with a START condition and terminated with a STOP condition.
• Acknowledge (A): Each receiving device, when addressed, is obliged to generate an acknowledge
after the reception of each byte. The master device must generate an extra clock pulse, which is
associated with this Acknowledge bit. The device that acknowledges has to pull down the SDA line
during the acknowledge clock pulse in such a way that the SDA line is stable LOW during the HIGH
period of the acknowledge-related clock pulse. Of course, setup and hold times must be taken into
account. During reads, a master must signal an end of data to the slave by not generating an
Acknowledge bit on the last byte that has been clocked out of the slave. In this case, the slave
(78M6610+PSU) will leave the data line HIGH to enable the master to generate the STOP condition.
1
2
7 8
9
ACK
MSB
Start Bit Start or Stop Bits
SCL may be held low by
slave to service interrupts
SCL
SDA
9
ACK
Device Addressing
A control byte is the first byte received following the START condition from the master device.
The control byte consists of a seven bit address and a bit (LSB) indicating the type of access (0=write;
1=read).
S X
X
X R/W
X
X X X
ACK
START BIT
DEVICE ADDRESS
LSB MSB
READ/WRITE
ACKNOWLEDGE
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