Samsung S3C2451X User Manual page 409

S3C2451X RISC MICROPROCESSOR
IIC-BUS INTERFACE
The S3C2451X IIC-bus interface has four operation modes:
— Master transmitter mode
— Master receive mode
— Slave transmitter mode
— Slave receive mode
Functional relationships among these operating modes are described below.
START AND STOP CONDITIONS
When the IIC-bus interface is inactive, it is usually in Slave mode. In other words, the interface should be in Slave
mode before detecting a Start condition on the SDA line (a Start condition can be initiated with a High-to-Low
transition of the SDA line while the clock signal of SCL is High). When the interface state is changed to Master
mode, a data transfer on the SDA line can be initiated and SCL signal generated.
A Start condition can transfer a one-byte serial data over the SDA line, and a Stop condition can terminate the
data transfer. A Stop condition is a Low-to-High transition of the SDA line while SCL is High. Start and Stop
conditions are always generated by the master. The IIC-bus gets busy when a Start condition is generated. A
Stop condition will make the IIC-bus free.
When a master initiates a Start condition, it should send a slave address to notify the slave device. One byte of
address field consists of a 7-bit address and a 1-bit transfer direction indicator (showing write or read).
If bit 8 is 0, it indicates a write operation (transmit operation); if bit 8 is 1, it indicates a request for data read
(receive operation).
The master will complete the transfer operation by transmitting a Stop condition. If the master wants to continue
the data transmission to the bus, it should generate another Start condition as well as a slave address. In this
way, the read-write operation can be performed in various formats.
SDA
SCL
Condition
Start
Figure 18-2. Start and Stop Condition
Preliminary product information describe products that are in development,
for which full characterization data and associated errata are not yet available.
Specifications and information herein are subject to change without notice.
IIC-BUS INTERFACE
SDA
SCL
Stop
Condition
18-3