140
AT94KAL Series FPSLIC
Rev. 1138G–FPSLI–11/03
Table 42.
Status Codes for Master Receiver 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+R
X
0
1
X
SLA+R will be transmitted
ACK or NOT ACK will be received
$10
A repeated START
condition has been
transmitted
Load SLA+R or
Load SLA+W
X
X
0
0
1
1
X
X
SLA+R will be transmitted
ACK or NOT ACK will be received
SLA+W will be transmitted
Logic will switch to Master Transmitter mode
$38
Arbitration lost in
SLA+R or NOT ACK bit
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 will be entered
A START condition will be transmitted when
the bus becomes free
$40
SLA+R has been
transmitted;
ACK has been received
No TWDR action or
No TWDR action
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK will
be returned
Data byte will be received and ACK will be
returned
$48
SLA+R has been
transmitted;
NOT ACK has been
received
No TWDR action or
No TWDR action or
No TWDR action
1
0
1
0
1
1
1
1
1
X
X
X
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
$50
Data byte has been
received;
ACK has been returned
Read data byte or
Read data byte
0
0
0
0
1
1
0
1
Data byte will be received and NOT ACK will
be returned
Data byte will be received and ACK will be
returned
$58
Data byte has been
received;
NOT ACK has been
returned
Read data byte or
Read data byte or
Read data byte
1
0
1
0
1
1
1
1
1
X
X
X
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