ATMEGA165P_0611 Datasheet, PDF (157/368 Pages) ATMEL Corporation – 8-bit Microcontroller with 16K Bytes In-System Programmable Flash

ATmega165P
17.4 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
17-3 and Figure 17-4. Data bits are shifted out and latched in on opposite edges of the SCK sig-
nal, ensuring sufficient time for data signals to stabilize. This is clearly seen by summarizing
Table 17-3 and Table 17-4, as done below:
Table 17-2. CPOL Functionality
Leading Edge
CPOL=0, CPHA=0
Sample (Rising)
CPOL=0, CPHA=1
Setup (Rising)
CPOL=1, CPHA=0
Sample (Falling)
CPOL=1, CPHA=1
Setup (Falling)
Trailing eDge
Setup (Falling)
Sample (Falling)
Setup (Rising)
Sample (Rising)
SPI Mode
0
1
2
3
Figure 17-3. SPI Transfer Format with CPHA = 0
SCK (CPOL = 0)
mode 0
SCK (CPOL = 1)
mode 2
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0) MSB
LSB first (DORD = 1) 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
Figure 17-4. SPI Transfer Format with CPHA = 1
SCK (CPOL = 0)
mode 1
SCK (CPOL = 1)
mode 3
SAMPLE I
MOSI/MISO
CHANGE 0
MOSI PIN
CHANGE 0
MISO PIN
SS
MSB first (DORD = 0)
LSB first (DORD = 1)
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
8019H–AVR–11/06
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