UPD753108 Datasheet, PDF (241/459 Pages) NEC – 4-bit Single-chip Microcontrollers

CHAPTER 5 PERIPHERAL HARDWARE FUNCTION
(e) Acknowledge signal (ACK)
The acknowledge signal is used for confirmation of data reception between the transmitter and receiver.
Figure 5-78. Acknowledge Signal
(When output in synchronization with 11th SCK)
SCK
8 9 10 11
SB0, SB1
ACK
(When output in synchronization with 9th SCK)
SCK
89
SB0, SB1
ACK
The acknowledge signal is a one-shot pulse synchronized with the falling edge of SCK after 8-bit data has
been transferred, and can be synchronized with arbitrary assertion of SCK.
The transmitter side checks, after it has transmitted 8-bit data, whether the receiver side returns an
acknowledge signal. If the acknowledge signal is not returned in a fixed time period after the data has
been transmitted, it is judged that the data has not been received correctly.
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