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S3C2440A RISC MICROPROCESSOR IIC-BUS INTERFACE
20-5
SDA
Acknowledgement
Signal from Receiver
SCL
S
1
2789 12 9
Acknowledgement
Signal from Receiver
MSB
ACK
Byte Complete, Interrupt
within Receiver
Clock Line Held Low by
receiver and/or transmitter
Figure 20-4. Data Transfer on the IIC-Bus
ACK SIGNAL TRANSMISSION
To complete a one-byte transfer operation, the receiver should send an ACK bit to the transmitter. The ACK pulse
should occur at the ninth clock of the SCL line. Eight clocks are required for the one-byte data transfer. The master
should generate the clock pulse required to transmit the ACK bit.
The transmitter should release the SDA line by making the SDA line High when the ACK clock pulse is received.
The receiver should also drive the SDA line Low during the ACK clock pulse so that the SDA keeps Low during the
High period of the ninth SCL pulse.
The ACK bit transmit function can be enabled or disabled by software (IICSTAT). However, the ACK pulse on the
ninth clock of SCL is required to complete the one-byte data transfer operation.
Data Output by
Transmitter
Data Output by
Receiver
SCL from
Master
Start
Condition
Clock Pulse for Acknowledgment
Clock to Output
987
S
1 2
Figure 20-5. Acknowledge on the IIC-Bus