2022年SPI四種模式區(qū)別資料

1、SPI 四 種 模 式 區(qū) 別精品資料spi 四種模式 SPI 的相位 CPHA和極性 CPOL分別可以為0 或 1,對應的4 種組合構成了SPI 的 4 種模式mode Mode 0 CPOL=0, CPHA=0 Mode 1 CPOL=0, CPHA=1 Mode 2 CPOL=1, CPHA=0 Mode 3 CPOL=1, CPHA=1 時鐘極性 CPOL: 即 SPI 閑暇時,時鐘信號SCLK 的電平（ 1: 閑暇時高電平 ; 0: 閑暇時低電平）時鐘相位 CPHA: 即 SPI 在 SCLK第幾個邊沿開頭采樣（0: 第一個邊沿開頭 ; 1: 其次個邊沿開頭）sd 卡地 spi 常用

2、的是 mode 0 和 mode 3 ,這兩種模式的相同的地方是都在時鐘上升沿采樣傳輸數(shù)據(jù),區(qū)別這兩種方式的簡潔方法就是看閑暇時,時鐘的電平狀態(tài),低電平為mode 0 ,高電平為mode 3 ；Overview The SPI standard includes four modes, defined by the polarity of SCLK and the phase relationship between data and SCLK. The clock polarity CPOL is determined by the idle state of SCLK. If the id

3、le state is low, CPOL is 0. If the idle state is high, CPOL is 1. The clock phase CPHA is determined by which edge that data is valid. If the data is valid on the first edge of SCLK, CPHA is 0. If the data is valid on the second edge of SCLK, CPHA is 1. Industry has two common formats to define the

4、four SPI modes. The first format defines the four possible combinations of phase and polarity as mode 0, mode 1, mode 2, and mode 3. The second format defines the combinations as mode 0,0, mode 0,1, mode 1,0, and mode 1,1. The SPI master must use a mode supported by the slave device to allow proper

5、communications. Dallas Semiconductor/Maxims SPI-interface RTCs support both SCLK polarities. The RTC automatically determines the polarity by detecting the idle state of SCLK when CE is asserted. The master must, therefore, place SCLK in the proper idle state before CE is asserted. Only one phase is

6、 supported. Since two SCLK polarities are supported, two of the four SPI modes are supported by the RTCs: modes 1 and 3 mode 0,1 and mode 1,1. On microcontrollers with built-in SPI interfaces, an SPI control or configuration register will have bits that control the polarity and phase. Because the RT

7、C supports either polarity, the polarity can be set as desired. The phase bit, however, must be set properly, or the RTC will not operate correctly. Figure 1 shows a typical single-byte read and Figure 2 shows a typical single-byte write. Each time CE is asserted, the first eight SCLK pulses are use

8、d to clock in a command byte. The command byte consists of several bits that define a register address, and one bit that 僅供學習與溝通,如有侵權請聯(lián)系網(wǎng)站刪除 感謝2 精品資料defines the data direction: a write if the next eight SCLK pulses will clock data into the part, or a read if data is clocked out of the part. Addition

9、al groups of eight SCLK pulses continue to transfer data in the selected direction until CE is deasserted. Note: In burst mode, CE is kept high and additional SCLK cycles are sent until the end of the burst. Figure 1. Single-byte read.Note: In burst mode, CE is kept high and additional SCLK cycles are sent until the end of the burst. Figure 2. Single-byte write.Examples of SPI code are available at: Real-Time Clocks Summary 僅供學習與溝通,如有侵權請聯(lián)系網(wǎng)