Table 24-3. Status Codes for Slave Receiver Mode
Status Code
(TWSR)
Prescaler Bits
are 0
Application Software Response
To TWCR
STO TWINT
Status of the 2-wire Serial Bus and
2-wire Serial Interface Hardware
To/from TWDR
STA
X
TWEA
0
Next Action Taken by TWI Hardware
0x60
0x68
0x70
0x78
Own SLA+W has been received;
ACK has been returned
No TWDR action or
0
1
Data byte will be received and NOT ACK will be
returned
No TWDR action
X
X
0
0
1
1
1
0
Data byte will be received and ACK will be returned
Arbitration lost in SLA+R/W as No TWDR action or
Master; own SLA+W has been
Data byte will be received and NOT ACK will be
returned
received; ACK has been returned
No TWDR action
X
X
0
0
1
1
1
0
Data byte will be received and ACK will be returned
General call address has been
received; ACK has been returned
No TWDR action or
Data byte will be received and NOT ACK will be
returned
No TWDR action
X
X
0
0
1
1
1
0
Data byte will be received and ACK will be returned
Arbitration lost in SLA+R/W as No TWDR action or
Master; General call address has
Data byte will be received and NOT ACK will be
returned
been received; ACK has been
returned
No TWDR action
X
X
0
0
1
1
1
0
Data byte will be received and ACK will be returned
0x80
0x88
Previously addressed with own Read data byte or
SLA+W; data has been received;
Data byte will be received and NOT ACK will be
returned
ACK has been returned
Read data byte
X
0
0
0
1
1
1
0
Data byte will be received and ACK will be returned
Previously addressed with own Read data byte or
SLA+W; data has been received;
NOT ACK has been returned
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
Read data byte or
0
1
0
0
1
1
1
0
Read data byte or
Read data byte
1
0
0
1
1
1
0
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
0x90
0x98
Previously addressed with
general call; data has been re-
ceived; ACK has been returned
Read data byte or
X
Data byte will be received and NOT ACK will be
returned
Read data byte
X
0
0
0
1
1
1
0
Data byte will be received and ACK will be returned
Previously addressed with
general call; data has been
received; NOT ACK has been
returned
Read data byte or
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
Read data byte or
Read data byte or
0
1
0
0
1
1
1
0
Read data byte
1
0
1
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
0xA0
A
STOP condition or repeated No action
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;
START condition has been
received while still addressed as
Slave
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
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
260
ATmega640/1280/1281/2560/2561
2549L–AVR–08/07
ATMEL [ ATMEL ]
