ATmega48/88/168
Figure 92. Formats and States in the Master Receiver Mode
MR
Successfull
reception
S
SLA
R
A
DATA
A
DATA
A
P
from a slave
receiver
$08
$40
$50
$58
Next transfer
started with a
repeated start
condition
RS
SLA
R
$10
Not acknowledge
received after the
slave address
W
A
P
$48
MT
Arbitration lost in slave
address or data byte
Other master
continues
Other master
continues
A or A
A
$38
A
$38
Arbitration lost and
addressed as slave
Other master
continues
To corresponding
states in slave mode
$68 $78 $B0
Any number of data bytes
and their associated acknowledge bits
From master to slave
From slave to master
DATA
A
This number (contained in TWSR) corresponds
to a defined state of the 2-Wire Serial Bus. The
prescaler bits are zero or masked to zero
n
Slave Receiver Mode
In the Slave Receiver mode, a number of data bytes are received from a Master Trans-
mitter (see Figure 93). All the status codes mentioned in this section assume that the
prescaler bits are zero or are masked to zero.
Figure 93. Data transfer in Slave Receiver mode
VCC
Device 1
SLAVE
RECEIVER
Device 2
MASTER
TRANSMITTER
Device 3
Device n
R1
R2
........
SDA
SCL
To initiate the Slave Receiver mode, TWAR and TWCR must be initialized as follows:
TWAR
TWA6
TWA5
TWA4
TWA3
TWA2
TWA1
TWA0
TWGCE
value
Device’s Own Slave Address
219
2545D–AVR–07/04
ATMEL [ ATMEL ]
