Rainbow Electronics AT91CAP9S250A - Manual (Page 460)

460
6264A–CAP–21-May-07
AT91CAP9S500A/AT91CAP9S250A
four possible combinations that are incompatible with one another. Thus, a master/slave pair
must use the same parameter pair values to communicate. If multiple slaves are used and
fixed in different configurations, the master must reconfigure itself each time it needs to com-
municate with a different slave.
Table 33-2 shows the four modes and corresponding parameter settings.
Figure 33-3 and Figure 33-4 show examples of data transfers.
Figure 33-3. SPI Transfer Format (NCPHA = 1, 8 bits per transfer)
Table 33-2. SPI Bus Protocol Mode
SPI Mode CPOL NCPHA
0 0 1
1 0 0
2 1 1
3 1 0
6
*
SPCK
(CPOL = 0)
SPCK
(CPOL = 1)
MOSI
(from master)
MISO
(from slave)
NSS
(to slave)
SPCK cycle (for reference)
MSB
MSB
LSB
LSB
6
6
5
5
4
4
3
3
2
2
1
1
* Not defined, but normally MSB of previous character received.
1 2 3 4 5 7 8 6