I
2
C Interface
MCF52277 Reference Manual, Rev. 1
31-8
Freescale Semiconductor
Figure 31-7. I
2
C Standard Communication Protocol
31.3.2
Slave Address Transmission
The master sends the slave address in the first byte after the START signal (B). After the seven-bit calling
address, it sends the R/W bit (C), which tells the slave data transfer direction (0 equals write transfer, 1
equals read transfer).
Each slave must have a unique address. An I
2
C master must not transmit its own slave address; it cannot
be master and slave at the same time.
The slave whose address matches that sent by the master pulls I2C_SDA low at the ninth serial clock (D)
to return an acknowledge bit.
31.3.3
Data Transfer
When successful slave addressing is achieved, data transfer can proceed (see E in
byte-by-byte basis in the direction specified by the R/W bit sent by the calling master.
Data can be changed only while I2C_SCL is low and must be held stable while I2C_SCL is high, as
shows. I2C_SCL is pulsed once for each data bit, with the msb being sent first. The receiving
device must acknowledge each byte by pulling I2C_SDA low at the ninth clock; therefore, a data byte
transfer takes nine clock pulses. See
Figure 31-8. Data Transfer
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
9 9
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
XXX
D7
D6
D5
D4
D3
D2
D1
D0
Calling Address
R/W
ACK
Bit
Data Byte
No
ACK
Bit
STOP
Signal
lsb
msb
lsb
msb
START
Signal
A
B
D
C
E
F
Interrupt bit set
(Byte complete)
I2C_SCL
I2C_SDA
I2C_SCL held low while
Interrupt is serviced
1
2
3
4
5
6
7
8
9
5
6
7
8
4
3
2
1
Bit6
Bit4
Bit3
Bit2
Bit1
Bit5
Bit7
Bit0
Bit6
Bit4
Bit3
Bit2
Bit1
Bit5
Bit0
Bit7
START
Signal
ACK from
Receiver
STOP
No
ACK Bit
Data Byte
Slave Address
R/W
Signal
Interrupt Bit Set
(Byte Complete)
9
I2C_SCL
I2C_SDA
I2C_SCL held low while
Interrupt is serviced
Summary of Contents for MCF52277
Page 22: ...MCF52277 Reference Manual Rev 1 Freescale Semiconductor xxii...
Page 32: ...MCF52277 Reference Manual Rev 0 xxxii Freescale Semiconductor...
Page 60: ...Signal Descriptions MCF52277 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 128: ...Static RAM SRAM MCF52277 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 140: ...Clock Module MCF52277 Reference Manual Rev 1 7 12 Freescale Semiconductor...
Page 172: ...Chip Configuration Module CCM MCF52277 Reference Manual Rev 1 9 16 Freescale Semiconductor...
Page 180: ...Serial Boot Facility SBF MCF52277 Reference Manual Rev 1 10 8 Freescale Semiconductor...
Page 188: ...Reset Controller Module MCF52277 Reference Manual Rev 1 11 8 Freescale Semiconductor...
Page 210: ...Crossbar Switch XBS MCF52277 Reference Manual Rev 1 13 8 Freescale Semiconductor...
Page 542: ...FlexCAN MCF52277 Reference Manual Rev 1 23 32 Freescale Semiconductor...
Page 724: ...UART Modules MCF52277 Reference Manual Rev 1 30 34 Freescale Semiconductor...
Page 740: ...I2 C Interface MCF52277 Reference Manual Rev 1 31 16 Freescale Semiconductor...
Page 790: ...Debug Module MCF52277 Reference Manual Rev 1 32 50 Freescale Semiconductor...