Rainbow Electronics ATmega64L - Manual (Page 182)

182
ATmega16(L)
2466B–09/01
Table 74. Status Codes for Master Receiver Mode
Status Code
(TWSR)
Prescaler Bits
are 0
Status of the 2-wire Serial Bus
and 2-wire Serial Interface Hard-
ware
Application Software Response
Next Action Taken by TWI 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