Freescale Semiconductor MCF52277 Reference Manual page 734

2
I C Interface
msb
I2C_SCL
1 2
I2C_SDA
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
START
Signal
Various combinations of read/write formats are then possible:
• The first example in
The transfer direction is not changed.
• The second example in
At the moment of the first acknowledge, the master-transmitter becomes a master-receiver and the
slave-receiver becomes slave-transmitter.
• In the third example in
repeated START signal. This is to communicate with same slave in a different mode without
releasing the bus. The master transmits data to the slave first, and then the master reads data from
slave by reversing the R/W bit.
ST = Start
SP = Stop
A = Acknowledge (I2C_SDA low)
A = Not Acknowledge (I2C_SDA high)
Rept ST = Repeated Start
Example 1:
7bit Slave Address
ST
Example 2:
7bit Slave Address
ST
Note: No acknowledge on the last byte
Example 3:
7-bit Slave
ST
Address
31-10
lsb
3 4 5 6 7
Calling Address
R/W
Figure 31-10. Repeated START
Figure 31-11 is the case of master-transmitter transmitting to slave-receiver.
Figure 31-11 is the master reading the slave immediately after the first byte.
Figure 31-11, START condition and slave address are repeated using the
R/W
0 A
R/W
1 A
R/W
1 A Data
A
Master Reads from Slave
Figure 31-11. Data Transfer, Combined Format
MCF52277 Reference Manual, Rev. 1
msb
8 9 1 2
XX AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
New Calling Address
ACK Repeated
Bit START
Signal
A
From Master to Slave
From Slave to Master
A
Data
Data
A
R/W
7-bit Slave
Rept
0
A
Address
ST
lsb
3 4 5 6 7 8
R/W
Data A/A SP
Data A SP
Data
Data A
Master Writes to Slave
Freescale Semiconductor
9
No STOP
ACK Signal
Bit
A/A SP