
MC97F6108A User’s manual
16. Inter Integrated Circuit (I2C)
171
16.5
Acknowledge
The acknowledge related clock pulse is generated by the master. The transmitter releases the SDA line
(HIGH) during the acknowledge clock pulse. The receiver must pull down the SDA line during the
acknowledge clock pulse so that it remains stable LOW during the HIGH period of this clock pulse.
When a slave is addressed by a master (Address Packet), and if it is unable to receive or transmit
because it’s performing some real time function, the data line must be left HIGH by the slave. And also,
when a slave addressed by a master is unable to receive more data bits, the slave receiver must release
the SDA line (Data Packet).
The master can then generate either a STOP condition to abort the transfer, or a repeated START
condition to start a new transfer.
If a master receiver is involved in a transfer, it must signal the end of data to the slave transmitter by
not generating an acknowledge on the last byte that was clocked out of the slave. The slave transmitter
must release the data line to allow the master to generate a STOP or repeated START condition.
Figure 79. Acknowledge on the I2C-Bus
1
2
8
Data Output by Transmitter
9
ACK
NAC
K
Clock pulse for ACK
Data Output by Receiver
SCL from MASTER