138
AT94KAL Series FPSLIC
Rev. 1138G–FPSLI–11/03
Table 41.
Status Codes for Master Transmitter Mode
Status
Code
(TWSR)
Status of the 2-wire
Serial Bus and 2-wire
Serial Hardware
Application Software Response
Next Action Taken by 2-wire
Serial Hardware
To/From TWDR
To TWCR
STA
STO
TWINT
TWEA
$08
A START condition
has been transmitted
Load SLA+W
X
0
1
X
SLA+W will be transmitted;
ACK or NOT ACK will be received
$10
A repeated START
condition has been
transmitted
Load SLA+W or
Load SLA+R
X
X
0
0
1
1
X
X
SLA+W will be transmitted;
ACK or NOT ACK will be received
SLA+R will be transmitted;
Logic will switch to Master Receiver mode
$18
SLA+W has been
transmitted;
ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$20
SLA+W has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$28
Data byte has been
transmitted;
ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$30
Data byte has been
transmitted;
NOT ACK has been
received
Load data byte or
No TWDR action or
No TWDR action or
No TWDR action
0
1
0
1
0
0
1
1
1
1
1
1
X
X
X
X
Data byte will be transmitted and ACK or NOT
ACK will be received
Repeated START will be transmitted
STOP condition will be transmitted and
TWSTO flag will be reset
STOP condition followed by a START
condition will be transmitted and TWSTO flag
will be reset
$38
Arbitration lost in
SLA+W or data bytes
No TWDR action or
No TWDR action
0
1
0
0
1
1
X
X
2-wire serial bus will be released and not
addressed Slave mode entered
A START condition will be transmitted when
the bus becomes free