upd70f3017ay Renesas Electronics Corporation., upd70f3017ay Datasheet - Page 247

• Manufacturer Part Number: upd70f3017ay
• Description: V850/sa1tm 32-/16-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

(4) Acknowledge signal (ACK)
The acknowledge signal (ACK) is used by the transmitting and receiving devices to confirm serial data reception.
The receiving device returns one ACK signal for every 8 bits of data it receives. The transmitting device normally
receives an ACK signal after transmitting 8 bits of data. However, when the master device is the receiving device,
it does not output an ACK signal after receiving the final data to be transmitted. The transmitting device detects
whether or not an ACK signal is returned after it transmits 8 bits of data. When an ACK signal is returned, the
reception is judged as normal and processing continues. If the slave device does not return an ACK signal, the
master device outputs either a stop condition or a restart condition and then stops the current transmission.
Failure to return an ACK signal may be caused by the following two factors.
When the receiving device sets the SDA line to low level during the ninth clock, the ACK signal becomes active
(normal receive response).
When bit 2 (ACKE) of IIC control register 0 (IICC0) is set to 1, automatic ACK signal generation is enabled.
Transmission of the eighth bit following the 7 address data bits causes bit 3 (TRC) of IIC status register 0 (IICS0)
to be set. When this TRC bit’s value is 0, it indicates receive mode. Therefore, ACKE should be set to 1.
When the slave device is receiving (when TRC = 0), if the slave device does not need to receive any more data
after receiving several bytes, setting ACKE to 0 will prevent the master device from starting transmission of the
subsequent data.
Similarly, when the master device is receiving (when TRC = 0) and the subsequent data is not needed and when
either a restart condition or a stop condition should therefore be output, setting ACKE to 0 will prevent the ACK
signal from being returned.
transmission) during transmission from the slave device.
(a) Reception was not performed normally.
(b) The final data was received.
SDA
SCL
CHAPTER 10
This prevents the MSB data from being output via the SDA line (i.e., stops
AD6
1
AD5
Figure 10-12. ACK Signal
User’s Manual U12768EJ4V1UD
2
AD4
SERIAL INTERFACE FUNCTION
3
AD3
4
AD2
5
AD1
6
AD0
7
R/W ACK
8
9
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