ATMEGA8L ATMEL [ATMEL Corporation], ATMEGA8L Datasheet - Page 186

• Manufacturer Part Number: ATMEGA8L
• Description: 8-bit AVR with 8K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Table 69. Status Codes for Slave Transmitter Mode
186
Status Code
(TWSR)
Prescaler Bits
are 0
0xA8
0xB0
0xB8
0xC0
0xC8
ATmega8(L)
Status of the Two-wire Serial Bus
and
Hardware
Own SLA+R has been received;
ACK has been returned
Arbitration lost in SLA+R/W as
Master; own SLA+R has been
received; ACK has been returned
Data byte in TWDR has been
transmitted; ACK has been
received
Data byte in TWDR has been
transmitted; NOT ACK has been
received
Last data byte in TWDR has been
transmitted (TWEA = “0”); ACK
has been received
Two-wire
Serial
Interface
In all sleep modes other than Idle mode, the clock system to the TWI is turned off. If the
TWEA bit is set, the interface can still acknowledge its own slave address or the general
call address by using the Two-wire Serial Bus clock as a clock source. The part will then
wake up from sleep and the TWI will hold the SCL clock will low during the wake up and
until the TWINT Flag is cleared (by writing it to one). Further data transmission will be
carried out as normal, with the AVR clocks running as normal. Observe that if the AVR is
set up with a long start-up time, the SCL line may be held low for a long time, blocking
other data transmissions.
Note that the Two-wire Serial Interface Data Register – TWDR does not reflect the last
byte present on the bus when waking up from these sleep modes.
To/from TWDR
Load data byte or
Load data byte
Load data byte or
Load data byte
Load data byte or
Load data byte
No TWDR action or
No TWDR action or
No TWDR action or
No TWDR action
No TWDR action or
No TWDR action or
No TWDR action or
No TWDR action
Application Software Response
STA
X
X
X
X
X
X
0
0
1
1
0
0
1
1
STO
0
0
0
0
0
0
0
0
0
0
0
0
0
0
To TWCR
TWINT
1
1
1
1
1
1
1
1
1
1
1
1
1
1
TWEA
0
1
0
1
0
1
0
1
0
1
0
1
0
1
Next Action Taken by TWI Hardware
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
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
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
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
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
2486M–AVR–12/03