MCF5282UM Datasheet, PDF (464/766 Pages) Freescale Semiconductor, Inc – MCF5282 and MCF5216 ColdFire Microcontroller User s Manual

I²C Interface
I2C_SCL
msb
lsb
1 2 34 5 67 89
msb
lsb
1 234 5 678 9
I2C_SDA
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
XX
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
START
Signal
Calling Address
R/W ACK
Bit
Repeated
START
Signal _A
New Calling Address
R/W No STOP
ACK Signal
Bit
Figure 24-10. Repeated START
Various combinations of read/write formats are then possible:
• The first example in Figure 24-11 is the case of master-transmitter transmitting to slave-receiver.
The transfer direction is not changed.
• The second example in Figure 24-11 is the master reading the slave immediately after the first byte.
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 Figure 24-11, START condition and slave address are repeated using the
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
From Master to Slave
From Slave to Master
Example 1:
ST 7bit Slave Address
R/W
0A
Data
A Data A/A SP
Example 2:
ST 7bit Slave Address
Note: No acknowledge on the last byte
R/W
1A
Data
A Data A SP
Example 3:
ST ^{7-bit Slave}
Address
R/W
1A
Data
R/W
A
Rept
ST
7-bit Slave
Address
0A
Data
A Data A/A SP
Master Reads from Slave
Master Writes to Slave
Figure 24-11. Data Transfer, Combined Format
24-10
MCF5282 and MCF5216 ColdFire Microcontroller User’s Manual, Rev. 3
Freescale Semiconductor