Datasheet

ATmega48/88/168 Automotive [DATASHEET]
7530K–AVR–07/14
190
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 of the bus.
Table 19-4. Status Codes for Master Transmitter 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+W 0 0 1 X SLA+W will be transmitted;
ACK or NOT ACK will be received
0x10 A repeated START
condition has been
transmitted
Load SLA+W
or
Load SLA+R
0
0
0
0
1
1
X
X
SLA+W will be transmitted;
ACK or NOT ACK will be received
SLA+R will be transmitted;
logic will switch to master receiver mode
0x18 SLA+W has been
transmitted;
ACK has been received
Load data byte or
No TWDR action
or No TWDR
action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or
NOT ACK will be received
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
0x20 SLA+W has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action
or No TWDR
action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or
NOT ACK will be received
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
0x28 Data byte has been
transmitted;
ACK has been received
Load data byte or
No TWDR action
or No TWDR
action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or
NOT ACK will be received
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
0x30 Data byte has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action
or No TWDR
action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or
NOT ACK will be received
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
0x38 Arbitration lost in SLA+W
or data bytes
No TWDR action
or
No TWDR action
0
1
0
0
1
1
X
X
2-wire serial bus will be released and not
addressed slave mode entered
A START condition will be transmitted when
the bus becomes free