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Chapter 22 Inter-Integrated Circuit Bus Controller Module (I
2
C)
MPC5606BK Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor
411
22.5
Functional description
22.5.1
I-Bus protocol
The I
2
C 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 logical AND function is
exercised on both lines with external pullup 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 and STOP signal. They are described briefly in the following sections and illustrated in
Figure 22-11. I
2
C bus transmission signals
22.5.1.1
START signal
When the bus is free, that is, no master device is engaging the bus (both SCL and SDA lines are at logical
high), a master may initiate communication by sending a START signal. As shown in
START signal is defined as a high-to-low transition of SDA while SCL is high. This signal denotes the
beginning of a new data transfer (each data transfer may contain several bytes of data) and brings all slaves
out of their idle states.
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
Summary of Contents for MPC5605BK
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Page 20: ...MPC5606BK Microcontroller Reference Manual Rev 2 20 Freescale Semiconductor...
Page 103: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 103 Clocks and power...
Page 645: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 643 Timers...
Page 715: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 713 ADC system...
Page 787: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 787 Memory...
Page 893: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 893 Integrity...
Page 943: ...MPC5606BK Microcontroller Reference Manual Rev 2 Freescale Semiconductor 943 Debug...