Atmel ATmega48A Manual page 237

Table 22-4. Status Codes for Slave Receiver Mode
Status Code
(TWSR) Status of the 2-wire Serial Bus
Prescaler Bits and 2-wire Serial Interface Hard-
are 0 ware
0x60 Own SLA+W has been received;
ACK has been returned
0x68 Arbitration lost in SLA+R/W as
Master; own SLA+W has been
received; ACK has been returned
0x70 General call address has been
received; ACK has been returned
0x78 Arbitration lost in SLA+R/W as
Master; General call address has
been received; ACK has been
returned
0x80 Previously addressed with own
SLA+W; data has been received;
ACK has been returned
0x88 Previously addressed with own
SLA+W; data has been received;
NOT ACK has been returned
0x90 Previously addressed with
general call; data has been re-
ceived; ACK has been returned
0x98 Previously addressed with
general call; data has been
received; NOT ACK has been
returned
0xA0 A STOP condition or repeated
START condition has been
received while still addressed as
Slave
8271D–AVR–05/11
ATmega48A/PA/88A/PA/168A/PA/328/P
Application Software Response
To/from TWDR
STA STO
No TWDR action or X
No TWDR action X
No TWDR action or X
No TWDR action X
No TWDR action or X
No TWDR action X
No TWDR action or X
No TWDR action X
Read data byte or X
Read data byte X
Read data byte or 0
Read data byte or 0
Read data byte or 1
Read data byte 1
Read data byte or X
Read data byte X
Read data byte or 0
Read data byte or 0
Read data byte or 1
Read data byte 1
No action 0
0
1
1
To TWCR
TWIN TWE
Next Action Taken by TWI Hardware
T A
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
0 1 1 Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = "1"
0 1 0 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
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
0 1 0 Data byte will be received and NOT ACK will be
returned
0 1 1 Data byte will be received and ACK will be returned
0 1 0 Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
0 1 1 Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = "1"
0 1 0 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
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
0 1 0 Switched to the not addressed Slave mode;
no recognition of own SLA or GCA
0 1 1 Switched to the not addressed Slave mode;
own SLA will be recognized;
GCA will be recognized if TWGCE = "1"
0 1 0 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
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
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