173
ATmega8A [DATASHEET]
8159E–AVR–02/2013
Table 21-8.
Formats and States in the Slave Transmitter Mode
Table 21-7.
Status Codes for Slave Transmitter Mode
Status Code
(TWSR)
Prescaler Bits
are 0
Status of the Two-wire Serial Bus
and Two-wire Serial Interface
Hardware
Application Software Response
Next Action Taken by TWI Hardware
To/from TWDR
To TWCR
STA
STO
TWINT
TWEA
0xA8
Own SLA+R has been received;
ACK has been returned
Load data byte or
Load data byte
X
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
0xB0
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
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
0xB8
Data byte in TWDR has been
transmitted; ACK has been
received
Load data byte or
Load data byte
X
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
0xC0
Data byte in TWDR has been
transmitted; NOT ACK has been
received
No TWDR action or
No TWDR action
0
1
0
1
0
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
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
0
1
0
1
0
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
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
S
SLA
R
A
DATA
A
$A8
$B8
A
$B0
Reception of the own
slave address and one or
more data bytes
Last data byte transmitted.
Switched to not addressed
slave (TWEA = '0')
Arbitration lost as master
and addressed as slave
n
From master to slave
From slave to master
Any number of data bytes
and their associated acknowledge bits
This number (contained in TWSR) corresponds
to a defined state of the Two-Wire Serial Bus. The
prescaler bits are zero or masked to zero
P or S
DATA
$C0
DATA
A
$C8
P or S
All 1's
A