AT90CAN128
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.
Table 93. Status Codes for Slave Transmitter Mode
Status Code
(TWSR)
Prescaler Bits
are 0
Application Software Response
Status of the Two-wire Serial Bus
and Two-wire Serial Interface
Hardware
To TWCR
To/from TWDR
STA
STO
0
TWINT
1
TWEA
0
Next Action Taken by TWI Hardware
0xA8
0xB0
0xB8
0xC0
Own SLA+R has been received;
ACK has been returned
Load data byte or
Load data byte
X
X
Last data byte will be transmitted and NOT ACK should
be received
Data byte will be transmitted and ACK should be re-
ceived
0
1
1
Arbitration lost in SLA+R/W as Load data byte or
master; own SLA+R has been
received; ACK has been returned
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
Load data byte
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 No TWDR action or
transmitted (TWEA = “0”); ACK
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;
has been received
No TWDR action or
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
1
1
0
0
1
1
0
1
No TWDR action
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
225
4250E–CAN–12/04
ATMEL [ ATMEL ]
