Datasheet
253
AT32UC3A
TXRDY used in Slave mode:
0 = As soon as data is written in the THR, until this data has been transmitted and acknowledged (ACK or NACK).
1 = It indicates that the THR is empty and that data has been transmitted and acknowledged.
If TXRDY is high and if a NACK has been detected, the transmission will be stopped. Thus when TRDY = NACK = 1, the
programmer must not fill THR to avoid losing it.
TXRDY behavior in Slave mode can be seen in Figure 24-23 on page 240, Figure 24-26 on page 242, Figure 24-28 on
page 244 and Figure 24-29 on page 244.
• SVREAD: Slave Read (automatically set / reset)
This bit is only used in Slave mode. When SVACC is low (no Slave access has been detected) SVREAD is irrelevant.
0 = Indicates that a write access is performed by a Master.
1 = Indicates that a read access is performed by a Master.
SVREAD behavior can be seen in Figure 24-23 on page 240, Figure 24-24 on page 241, Figure 24-28 on page 244 and
Figure 24-29 on page 244.
• SVACC: Slave Access (automatically set / reset)
This bit is only used in Slave mode.
0 = TWI is not addressed. SVACC is automatically cleared after a NACK or a STOP condition is detected.
1 = Indicates that the address decoding sequence has matched (A Master has sent SADR). SVACC remains high until a
NACK or a STOP condition is detected.
SVACC behavior can be seen in Figure 24-23 on page 240, Figure 24-24 on page 241, Figure 24-28 on page 244 and Fig-
ure 24-29 on page 244.
• GACC: General Call Access (clear on read)
This bit is only used in Slave mode.
0 = No General Call has been detected.
1 = A General Call has been detected. After the detection of General Call, the programmer decoded the commands that fol-
low and the programming sequence.
GACC behavior can be seen in Figure 24-25 on page 241.
• OVRE: Overrun Error (clear on read)
This bit is only used in Master mode.
0 = RHR has not been loaded while RXRDY was set
1 = RHR has been loaded while RXRDY was set. Reset by read in SR when TXCOMP is set.
• NACK: Not Acknowledged (clear on read)
NACK used in Master mode:
0 = Each data byte has been correctly received by the far-end side TWI slave component.
1 = A data byte has not been acknowledged by the slave component. Set at the same time as TXCOMP.
32058K
AVR32-01/12