Datasheet

197
ATmega48PA/88PA/168PA [DATASHEET]
9223F–AVR–04/14
Table 22-4. 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 HardwareTo/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
1
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