Datasheet

ATmega48PA/88PA/168PA [DATASHEET]
9223F–AVR–04/14
194
Table 22-3. 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 HardwareTo/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