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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
(d) Acknowledge signal (ACK)
The acknowledge signal indicates that the transferred serial data has definitely been received. This signal
is used between the transmitting side and receiving side devices for confirmation of correct data transfer.
In principle, the receiving side device returns an acknowledge signal to the transmitting device each time
it receives 8-bit data. The only exception is when the receiving side is the master device and the 8-bit
data is the last transfer data; the master device outputs no acknowledge signal in this case.
The transmitting side that has transferred 8-bit data waits for the acknowledge signal which will be sent
from the receiving side. If the transmitting side device receives the acknowledge signal, which means
a successful data transfer, it proceeds to the next processing. If this signal is not sent back from the slave
device, this means that the data sent has not been received by the slave device, and therefore the master
device outputs a stop condition signal to terminate subsequent transmissions.
Figure 13-40. Acknowledge Signal
(e) Stop condition
If the SDA0 (SDA1) pin level changes from low to high while the SCL pin is high, this transition is defined
as a stop condition signal.
The stop condition signal is output from the master to the slave device to terminate a serial transfer.
The stop condition signal is detected by hardware incorporated in the slave device.
Figure 13-41. Stop Condition
1
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5
6
7
A6
A5
A4
A3
A2
A1
A0
R/W
SCL
SDA0 (SDA1)
9
8
ACK
H
SCL
SDA0 (SDA1)