Datasheet

193
ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
After a repeated START condition (state 0x10) the 2-wire serial interface can access the same slave again, or a new slave
without transmitting a STOP condition. Repeated START enables the master to switch between slaves, master transmitter
mode and master receiver mode without losing control over the bus.
Table 19-5. Status Codes for Master Receiver Mode
Status Code
(TWSR)
Prescaler
Bits are 0
Status of the 2-wire
Serial Bus and 2-wire
Serial Interface
Hardware
Application Software Response
Next Action Taken by TWI Hardware
To/from TWDR To TWCR
STA STO TWINT TWEA
0x08 A START condition has
been transmitted
Load SLA+R 0 0 1 X SLA+R will be transmitted
ACK or NOT ACK will be received
0x10 A repeated START
condition has been
transmitted
Load SLA+R
or
Load SLA+W
0
0
0
0
1
1
X
X
SLA+R will be transmitted
ACK or NOT ACK will be received
SLA+W will be transmitted Logic will switch
to master transmitter mode
0x38 Arbitration lost in SLA+R
or NOT ACK bit
No TWDR action
or
No TWDR action
0
0
0
0
1
1
X
X
2-wire serial bus will be released and not
addressed Slave mode will be entered
A START condition will be transmitted
when the bus becomes free
0x40 SLA+R has been
transmitted;
ACK has been received
No TWDR action
or
No TWDR action
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
0x48 SLA+R has been
transmitted;
NOT ACK has been
received
No TWDR action or
No TWDR action or
No TWDR action
1
0
1
0
1
1
1
1
1
X
X
X
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO
flag will be reset
0x50 Data byte has been
received;
ACK has been returned
Read data byte or
Read data byte
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK
will be returned
Data byte will be received and ACK will be
returned
0x58 Data byte has been
received;
NOT ACK has been
returned
Read data byte or
Read data byte
or
Read data byte
1
0
1
0
1
1
1
1
1
X
X
X
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO
flag will be reset