Transfer Direction Specification; Acknowledge Signal (Ack) - NEC V850ES/F 3-L Series User Manual

2
I C Bus (IIC)

17.6.3 Transfer direction specification

SCL0n
SDA0n
INTIICn
Figure 17-8
Note

17.6.4 Acknowledge signal (ACK)

In addition to the 7-bit address data, the master device sends 1 bit that
specifies the transfer direction. When this transfer direction specification bit
has a value of 0, it indicates that the master device is transmitting data to a
slave device. When the transfer direction specification bit has a value of 1, it
indicates that the master device is receiving data from a slave device.
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AD6 AD5 AD4
Transfer direction specification
The INTIICn signal is generated if a local address or extension code is
received during slave device operation.
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 each 8 bits of data it receives.
The transmitting device normally receives an ACK signal after transmitting 8
bits of data. The detection of ACK is confirmed with the IICS0.ACKD0 bit.
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 three factors:
• Reception was not performed normally.
• The final data was received.
• The receiving device (slave) does not exist for the specified address.
When the receiving device sets the SDA0n line to low level during the ninth
clock, the ACK signal becomes active (normal receive response).
When the IICCn.ACKEn bit is set to 1, automatic ACK signal generation is
enabled.
Transmission of the eighth bit following the 7 address data bits causes the
IICSn.TRCn bit to be set. When this TRCn bit's value is 0, it indicates receive
mode. Therefore, the ACKEn bit should be set to 1.
When the slave device is receiving (when TRCn bit = 0), if the slave device
does not need to receive any more data after receiving several bytes, clearing
User's Manual U18743EE1V2UM00
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Transfer direction specification
Chapter 17
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