AT32UC3C2512C Automotive Atmel Corporation, AT32UC3C2512C Automotive Datasheet - Page 737

• Manufacturer Part Number: AT32UC3C2512C Automotive
• Manufacturer: Atmel Corporation

9166C–AVR-08/11
The TWI transfers require the receiver to acknowledge each received data byte. During the
acknowledge clock pulse (9th pulse), the slave releases the data line (HIGH), enabling the mas-
ter to pull it down in order to generate the acknowledge. The slave polls the data line during this
clock pulse and sets the NAK bit in SR if the master does not acknowledge the data byte. A NAK
means that the master does not wish to receive additional data bytes. As with the other status
bits, an interrupt can be generated if enabled in the Interrupt Enable Register (IER).
SR.TXRDY is used as Transmit Ready for the Peripheral DMA Controller transmit channel.
The end of the complete transfer is marked by the SR.TCOMP bit changing from zero to one.
See
Figure 28-7. Slave Transmitter with One Data Byte
3. The data byte in the shifter is transmitted.
4. NBYTES is updated. If CR.CUP is one, NBYTES is incremented, otherwise NBYTES is
5. After each data byte has been transmitted, the master transmits an ACK (Acknowledge)
6. If STOP is received, SR.TCOMP and SR.STO will be set.
7. If REPEATED START is received, SR.REP will be set.
Figure 28-7
– SMBus mode and CR.PEC is one: If NBYTES is zero, the generated PEC byte is
decremented.
or NAK (Not Acknowledge) bit. If a NAK bit is received by the TWIS, the SR.NAK bit is
set. Note that this is done two CLK_TWIS cycles after TWCK has been sampled by the
TWIS to be HIGH (see
the TWIS will wait for a STOP or REPEATED START. If an ACK bit is received, the
SR.NAK bit remains LOW. The ACK indicates that more data should be transmitted,
jump to step 2. At the end of the ACK/NAK clock cycle, the Byte Transfer Finished
(SR.BTF) bit is set. Note that this is done two CLK_TWIS cycles after TWCK has been
sampled by the TWIS to be LOW (see
SR.NAK bit is set, it must not be cleared before the SR.BTF bit is set to ensure correct
TWIS behavior.
automatically transmitted instead of a data byte from THR. TWCK will not be
stretched by the TWIS.
TCOMP
TXRDY
TWD
Write THR (DATA)
and
NBYTES set to 1
S
Figure
DADR
28-8.
Figure
28-9). The NAK indicates that the transfer is finished, and
R
Figure
A
28-9). Also note that in the event that
DATA
N
STOP sent by master
P
AT32UC3C
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