Samsung S5PC110, Manual

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S5PC110_UM 2 IIC-BUS INTERFACE
2-3
2.3 I I C-BUS INTERFACE OPERATION
The S5PC110 I
2
C-bus interface has four operation modes, namely:
•
Master Transmitter Mode
•
Master Receive Mode
•
Slave Transmitter Mode
•
Slave Receive Mode
The functional relationships among these operating modes are described below.
2.3.1 START AND STOP CONDITIONS
If the I
2
C-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 is initiated with a High-to-Low transition
of the SDA line while the clock signal of SCL is High). If the interface state is changed to Master mode, SDA line
initiates data transfer and generates SCL signal.
A Start condition transfers one-byte serial data via SDA line, and a Stop condition terminates the data transfer. A
Stop condition is a Low-to-High transition of the SDA line while SCL is High. The master generates Start and Stop
conditions. The I
2
C-bus gets busy if a Start condition is generated. On the other hand, a Stop condition frees the
I
2
C-bus.
If 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 (that shows 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 transmits Stop condition to complete the transfer operation. 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 is performed in various formats.
SCL
SDA SDA
SCL
Start
Condition
Stop
Condition
Figure 2-2 Start and Stop Condition