SAM7S321_14 Datasheet, PDF (324/775 Pages) ATMEL Corporation – ARM-based Flash MCU

Figure 30-6. Master Write with One Data Byte
TWD S
DADR
W
A
DATA
A
P
TXCOMP
TXRDY
Write THR (DATA)
Figure 30-7. Master Write with Multiple Data Byte
TWD S
DADR
W
A
DATA n
A
TXCOMP
STOP sent automaticaly
(ACK received and TXRDY = 1)
DATA n+5
A
DATA n+x
A
P
TXRDY
Write THR (Data n)
Write THR (Data n+1)
Write THR (Data n+x)
Last data sent
STOP sent automaticaly
(ACK received and TXRDY = 1)
Figure 30-8. Master Write with One Byte Internal Address and Multiple Data Bytes
TWD S
DADR
W A IADR(7:0) A
DATA n
A
DATA n+5 A DATA n+x A P
TXCOMP
TXRDY
Write THR (Data n)
Write THR (Data n+1) Write THR (Data n+x) STOP sent automaticaly
Last data sent (ACK received and TXRDY = 1)
30.7.5 Master Receiver Mode
The read sequence begins by setting the START bit. After the start condition has been sent, the master sends a 7-
bit slave address to notify the slave device. The bit following the slave address indicates the transfer direction, 1 in
this case (MREAD = 1 in TWI_MMR). During the acknowledge clock pulse (9th pulse), the master releases the
data line (HIGH), enabling the slave to pull it down in order to generate the acknowledge. The master polls the data
line during this clock pulse and sets the NACK bit in the status register if the slave does not acknowledge the byte.
If an acknowledge is received, the master is then ready to receive data from the slave. After data has been
received, the master sends an acknowledge condition to notify the slave that the data has been received except for
the last data, after the stop condition. See Figure 30-9. When the RXRDY bit is set in the status register, a charac-
ter has been received in the receive-holding register (TWI_RHR). The RXRDY bit is reset when reading the
TWI_RHR.
When a single data byte read is performed, with or without internal address (IADR), the START and STOP bits
must be set at the same time. See Figure 30-9. When a multiple data byte read is performed, with or without inter-
SAM7S Series [DATASHEET]
6175M–ATARM–26-Oct-12
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