NEC 78014Y Series, User Manual

Page: 382 / 547

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CHAPTER 16 SERIAL INTERFACE CHANNEL 0 (
µ
PD78014Y Subseries)
382
(d) Acknowledge signal (ACK)
The acknowledge signal indicates that the transferred serial data has definitely been received. The receiving
side returns an acknowledge signal each time it receives 8-bit data.
The receiving side usually outputs after 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 sending side that has transferred 8-bit checks if the acknowledge signal has been sent from the receiving
side. If the sending 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 correctly by the slave device and therefore the master device outputs a stop
condition signal to terminate subsequent transmissions.
Figure 16-41. 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 16-42. Stop Condition
1 2 3 4 5 6 7
A6 A5 A4 A3 A2 A1 A0 R/W
SCL
SDA0 (SDA1)
9 8
ACK
“H”
SCL
SDA0 (SDA1)