ATmega88PA Automotive Atmel Corporation, ATmega88PA Automotive Datasheet - Page 216

• Manufacturer Part Number: ATmega88PA Automotive
• Manufacturer: Atmel Corporation

22.3.5
Figure 22-6. Typical Data Transmission
216
SDA
SCL
Atmel ATmega48PA/88PA/168PA [Preliminary]
START
Combining Address and Data Packets into a Transmission
Addr MSB
1
Figure 22-5. Data Packet Format
A transmission basically consists of a START condition, a SLA+R/W, one or more data pack-
ets and a STOP condition. An empty message, consisting of a START followed by a STOP
condition, is illegal. Note that the Wired-ANDing of the SCL line can be used to implement
handshaking between the Master and the Slave. The Slave can extend the SCL low period by
pulling the SCL line low. This is useful if the clock speed set up by the Master is too fast for the
Slave, or the Slave needs extra time for processing between the data transmissions. The
Slave extending the SCL low period will not affect the SCL high period, which is determined by
the Master. As a consequence, the Slave can reduce the TWI data transfer speed by prolong-
ing the SCL duty cycle.
Figure 22-6
between the SLA+R/W and the STOP condition, depending on the software protocol imple-
mented by the application software.
2
Transmitter
Aggregate
SDA from
SDA from
SCL from
Receiver
Master
SDA
SLA+R/W
SLA+R/W
Addr LSB
7
shows a typical data transmission. Note that several data bytes can be transmitted
R/W
8
Data MSB
ACK
9
1
2
Data MSB
1
Data Byte
2
7
Data Byte
Data LSB
8
7
Data LSB
ACK
9
8
ACK
9
STOP, REPEATED
START or Next
9223B–AVR–09/11
Data Byte
STOP