SPI Modes

Posted on One min read

There are 4 SPI modes defined by the clock polarity (CPOL) and the clock phase (CPHA) which defines which edge the data is sampled on.

MODE CPOL CPHA
0 0 0
1 0 1
2 1 0
3 1 1

SPI Mode 0 Waveforms

SCLK starts low. Data is sampled on rising edge.

{ 
  "signal": [ 
        {"name":"SCLK", "wave":"l.P.......l"},
        {
            "name":"MOSI", 
            "wave":"x22222222x.", "data":["0","1","2","3","4","5","6","7"], 
            "phase": -0.25 
        },
        {
            "name":"MISO", 
            "wave":"x22222222x.", "data":["0","1","2","3","4","5","6","7"],
            "phase": -0.25 
        },            
        {"name":"CS",   "wave":"10........1"}
]}

SPI Mode 1 Waveforms

SCLK starts low. Data is sampled on falling edge.

{ 
  "signal": [ 
        {"name":"SCLK", "wave":"l.p.......l"},
        {
            "name":"MOSI", 
            "wave":"xx22222222x", "data":["0","1","2","3","4","5","6","7"], 
            "phase": 0.25 
        },
        {
            "name":"MISO", 
            "wave":"xx22222222x", "data":["0","1","2","3","4","5","6","7"],
            "phase": 0.25 
        },            
        {"name":"CS",   "wave":"10........1"}
]}

SPI Mode 2 Waveforms

SCLK starts high. Data is sampled on falling edge.

{ 
  "signal": [ 
        {"name":"SCLK", "wave":"h.N.......h"},
        {
            "name":"MOSI", 
            "wave":"x22222222x.", "data":["0","1","2","3","4","5","6","7"], 
            "phase": -0.25 
        },
        {
            "name":"MISO", 
            "wave":"x22222222x.", "data":["0","1","2","3","4","5","6","7"],
            "phase": -0.25 
        },            
        {"name":"CS",   "wave":"10........1"}
]}

SPI Mode 3 Waveforms

SCLK starts high. Data is sampled on rising edge.

{ 
  "signal": [ 
        {"name":"SCLK", "wave":"h.n.......h"},
        {
            "name":"MOSI", 
            "wave":"x.22222222x", "data":["0","1","2","3","4","5","6","7"], 
            "phase": 0.25 
        },
        {
            "name":"MISO", 
            "wave":"x.22222222x", "data":["0","1","2","3","4","5","6","7"],
            "phase": 0.25 
        },            
        {"name":"CS",   "wave":"10........1"}
]}

Diagrams Courtesy WaveDrom

The diagrams above are displayed using the WaveDrom javascript library.