23.4.2.6.2 Host Mode Clocking and MCLK

The SPI module as a Host has the ability to generate BCLK and LRCK by internally generating using SPICLK (MCLKEN = 0). In addition, the 33A device can generate the clock for external codec devices using the reference output, REFCLKO, function (see Figure 23-29), although some codecs may have the ability to generate their own MCLK from a crystal to provide accurate audio sample rates. Figure 23-30 shows that the REFCLKO clock can be used as MCLKIN by the codec.

Figure 23-29. SPIx Host Clock Generation

Figure 23-30 shows the interface between an SPI client and a codec host, deriving the clock from the MCLK input interface.

Figure 23-30. SPIx Client and Codec Host – Clock Derived from MCLK