Start And Stop Conditions; Iic-Bus Interface - Samsung S3C2416 User Manual

S3C2416X RISC MICROPROCESSOR

1.1 IIC-BUS INTERFACE

The S3C2416 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.

1.2 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 17-2. Start and Stop Condition
IIC-BUS INTERFACE
SDA
SCL
Stop
Condition
17-3