Product Specs

Table Of Contents
48 SPI Serial peripheral interface master
Page
516
1
1
CSN
SCK
MOSI
MISO
CPU
Figure 151: SPI master transaction
The READY event of the third byte transaction is delayed until B is extracted from RXD in occurrence
number 3 on the horizontal lifeline. The reason for this is that the third event is generated first when C is
moved from RXD-1 to RXD after B is read.
The SPI master will move the incoming byte to the RXD register after a short delay following the SCK clock
period of the last bit in the byte. This also means that the READY event will be delayed accordingly, see
Figure 152: SPI master transaction on page 516. Therefore, it is important that you always clear the
READY event, even if the RXD register and the data that is being received is not used.
Figure 152: SPI master transaction
0
1
2
n-2
n-1
n
A
B
C
m-2
m-1
m
1
2
3 4
5
6
7
TXD = 0
TXD = 1
SCK
(CPHA=0)
Lifeline
MOSI
MISO
READY
CSN
READY
A = RXD
TXD = 2
SCK
(CPHA=1)
READY
B = RXD
TXD = n-2
C = RXD
TXD = n-1
Lifeline
MOSI
MISO
READY
CSN
READY
m-2 = RXD
TXD = n
READY
READY
READY
m-1 = RXD
m = RXD