MC68HC12 MOTOROLA [Motorola, Inc], MC68HC12 Datasheet - Page 306

• Manufacturer Part Number: MC68HC12
• Description: The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device composed of standard on-chip peripherals including a 16-bit central processing unit
• Manufacturer: MOTOROLA [Motorola, Inc]

Inter IC Bus
17.5.4 STOP Signal
17.5.5 Repeated START Signal
Technical Data
306
Each data byte is 8 bits long. Data may be changed only while SCL is
low and must be held stable while SCL is high as shown in
There is one clock pulse on SCL for each data bit, the MSB being
transferred first. Each data byte has to be followed by an acknowledge
bit, which is signalled from the receiving device by pulling the SDA low
at the ninth clock. So one complete data byte transfer needs nine clock
pulses.
If the slave receiver does not acknowledge the master, the SDA line
must be left high by the slave. The master can then generate a stop
signal to abort the data transfer or a start signal (repeated start) to
commence a new calling.
If the master receiver does not acknowledge the slave transmitter after
a byte transmission, it means 'end of data' to the slave, so the slave
releases the SDA line for the master to generate STOP or START signal.
The master can terminate the communication by generating a STOP
signal to free the bus. However, the master may generate a START
signal followed by a calling command without generating a STOP signal
first. This is called repeated START. A STOP signal is defined as a low-
to-high transition of SDA while SCL at logical “1” (see
The master can generate a STOP even if the slave has generated an
acknowledge at which point the slave must release the bus.
As shown in
generated without first generating a STOP signal to terminate the
communication. This is used by the master to communicate with another
slave or with the same slave in different mode (transmit/receive mode)
without releasing the bus.
Figure
Inter IC Bus
17-2, a repeated START signal is a START signal
MC68HC912DT128A — Rev 4.0
Figure
Figure
MOTOROLA
17-2).
17-2.