MC9S08AW16CFUE Datasheet, PDF (225/324 Pages) Freescale Semiconductor, Inc – MC9S08AW60 Features

Chapter 13 Inter-Integrated Circuit (S08IICV1)
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.
MSB
LSB
SCL
1 2 34 5 6 78 9
MSB
LSB
1 2 34 5 6 78 9
SDA
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
XXX D7 D6 D5 D4 D3 D2 D1 D0
START
SIGNAL
CALLING ADDRESS
READ/ ACK
WRITE ^BIT
MSB
LSB
SCL
1 2 34 5 67 89
DATA BYTE
NO STOP
ACK SIGNAL
BIT
MSB
LSB
1 234 5 678 9
SDA
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
XX
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
START
SIGNAL
CALLING ADDRESS
READ/ ACK REPEATED
WRITE ^{BIT START}
SIGNAL
NEW CALLING ADDRESS
READ/ NO STOP
WRITE
ACK
BIT
SIGNAL
Figure 13-8. IIC Bus Transmission Signals
MC9S08AW60 Data Sheet, Rev 2
Freescale Semiconductor
225