Datasheet

Chapter 13 Inter-Integrated Circuit (S08IICV1)
MC9S08AW60 Data Sheet, Rev 2
Freescale Semiconductor 225
13.4 Functional Description
This section provides a complete functional description of the IIC module.
13.4.1 IIC Protocol
The IIC bus system uses a serial data line (SDA) and a serial clock line (SCL) for data transfer. All devices
connected to it must have open drain or open collector outputs. A logic AND function is exercised on both
lines with external pull-up resistors. The value of these resistors is system dependent.
Normally, a standard communication is composed of four parts:
• START signal
• Slave address transmission
• Data transfer
• STOP signal
The STOP signal should not be confused with the CPU STOP instruction. The IIC bus system
communication is described briefly in the following sections and illustrated in Figure 13-8.
Figure 13-8. IIC Bus Transmission Signals
SCL
SDA
START
SIGNAL
ACK
BIT
12345678
MSB LSB
12345678
MSB LSB
STOP
SIGNAL
NO
SCL
SDA
1234567 8
MSB LSB
1 2 5 678
MSB LSB
REPEATED
34
99
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W XXX D7 D6 D5 D4 D3 D2 D1 D0
CALLING ADDRESS READ/ DATA BYTE
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
NEW CALLING ADDRESS
99
XX
ACK
BIT
WRITE
START
SIGNAL
START
SIGNAL
ACK
BIT
CALLING ADDRESS READ/
WRITE
STOP
SIGNAL
NO
ACK
BIT
READ/
WRITE