Inter-Integrated Circuit (S08IICV2)
MC9S08QE128 MCU Series Reference Manual, Rev. 2
228
Freescale Semiconductor
12.4
Functional Description
This section provides a complete functional description of the IIC module.
12.4.1
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 12-9. IIC Bus Transmission Signals
SCL
SDA
START
SIGNAL
ACK
BIT
1
2
3
4
5
6
7
8
MSB
LSB
1
2
3
4
5
6
7
8
MSB
LSB
STOP
SIGNAL
NO
SCL
SDA
1
2
3
4
5
6
7
8
MSB
LSB
1
2
5
6
7
8
MSB
LSB
REPEATED
3
4
9
9
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
9
9
XX
ACK
BIT
WRITE
START
SIGNAL
START
SIGNAL
ACK
BIT
CALLING ADDRESS
READ/
WRITE
STOP
SIGNAL
NO
ACK
BIT
READ/
WRITE
Содержание MC9S08QE128
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