Rainbow Electronics ATmega3290P_V - Manual (Page 160)

160
ATmega329/339/649/659
2552H–AVR–11/06
Data Modes There are four combinations of SCK phase and polarity with respect to serial data,
which are determined by control bits CPHA and CPOL. The SPI data transfer formats
are shown in Figure 68 and Figure 69. Data bits are shifted out and latched in on oppo-
site edges of the SCK signal, ensuring sufficient time for data signals to stabilize. This is
clearly seen by summarizing Table 73 and Table 74, as done below:
Figure 68. SPI Transfer Format with CPHA = 0
Figure 69. SPI Transfer Format with CPHA = 1
Table 76. CPOL Functionality
Leading Edge Trailing eDge SPI Mode
CPOL=0, CPHA=0 Sample (Rising) Setup (Falling) 0
CPOL=0, CPHA=1 Setup (Rising) Sample (Falling) 1
CPOL=1, CPHA=0 Sample (Falling) Setup (Rising) 2
CPOL=1, CPHA=1 Setup (Falling) Sample (Rising) 3
Bit 1
Bit 6 LSB
MSB
SCK (CPOL = 0)
mode 0
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SCK (CPOL = 1)
mode 2
SS
MSB
LSB Bit 6
Bit 1 Bit 5
Bit 2 Bit 4
Bit 3 Bit 3
Bit 4 Bit 2
Bit 5 MSB first (DORD = 0)
LSB first (DORD = 1)
SCK (CPOL = 0)
mode 1
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SCK (CPOL = 1)
mode 3
SS
MSB
LSB Bit 6
Bit 1 Bit 5
Bit 2 Bit 4
Bit 3 Bit 3
Bit 4 Bit 2
Bit 5 Bit 1
Bit 6 LSB
MSB MSB first (DORD = 0)
LSB first (DORD = 1)