mc9s12hz256v2 Freescale Semiconductor, Inc, mc9s12hz256v2 Datasheet - Page 323

• Manufacturer Part Number: mc9s12hz256v2
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

11.4
This section provides a complete functional description of the IIC.
11.4.1
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. 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 and STOP signal. They are described briefly in the following sections and illustrated in
Figure
11.4.1.1
When the bus is free, i.e. 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.
Freescale Semiconductor
SDA
11-8.
SCL
SDA
SCL
Signal
Signal
Start
Start
Functional Description
I-Bus Protocol
START Signal
MSB
MSB
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
1
1
2
2
Calling Address
Calling Address
3
3
4
4
5
5
Figure 11-8. IIC-Bus Transmission Signals
6
6
MC9S12HZ256 Data Sheet, Rev. 2.05
7
7
Read/
Read/
Write
Write
LSB
LSB
8
8
Ack
Ack
Bit
Bit
9
9
XX
Repeated
XXX
Signal
Start
MSB
MSB
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
D7
1
1
D6
2
2
New Calling Address
D5
3
3
Data Byte
D4
4
4
Chapter 11 Inter-Integrated Circuit (IICV2)
D3
5
5
D2
6
6
D1
7
7
Read/
Write
LSB
LSB
Figure
D0
8
8
Ack
No
Bit
Ack
9
No
9
Bit
11-8, a
Signal
Stop
Signal
Stop
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