Table 21-5. Status Codes for Slave Transmitter Mode
Status Code
(TWSR)
Prescaler
Bits
Application Software Response
To TWCR
STO TWIN
Status of the 2-wire Serial Bus
and 2-wire Serial Interface Hard-
ware
To/from TWDR
STA
TWE
A
Next Action Taken by TWI Hardware
T
are 0
0xA8
0xB0
0xB8
0xC0
Own SLA+R has been received;
ACK has been returned
Load data byte or
Load data byte
X
X
0
0
1
0
1
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
1
Arbitration lost in SLA+R/W as
Master; own SLA+R has been
received; ACK has been returned
Load data byte or
Load data byte
X
X
0
0
1
1
0
1
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
Data byte in TWDR has been
transmitted; ACK has been
received
Load data byte or
Load data byte
X
X
0
0
1
1
0
1
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
Data byte in TWDR has been
transmitted; NOT ACK has been
received
No TWDR action or
No TWDR action or
0
0
0
0
1
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = “1”
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA;
a START condition will be transmitted when the bus
becomes free
No TWDR action or
No TWDR action
1
1
0
0
1
1
0
1
Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = “1”;
a START condition will be transmitted when the bus
becomes free
0xC8
Last data byte in TWDR has been
transmitted (TWEA = “0”); ACK
has been received
No TWDR action or
No TWDR action or
0
0
0
0
1
1
0
1
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = “1”
Switched to the not addressed Slave mode;
no recognition of own SLA or GCA;
a START condition will be transmitted when the bus
becomes free
No TWDR action or
No TWDR action
1
1
0
0
1
1
0
1
Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = “1”;
a START condition will be transmitted when the bus
becomes free
234
ATmega48/88/168
2545M–AVR–09/07
ATMEL [ ATMEL ]
