configuration register
| CHLEN | Channel length (number of bits per audio channel)  |  
| DATLEN | Data length to be transferred  |  
| CKPOL | Inactive state clock polarity  |  
| I2SSTD | standard selection  |  
| PCMSYNC | PCM frame synchronization  |  
| I2SCFG | I2S configuration mode  |  
| SE2 | I2S enable  |  
| I2SMOD | I2S mode selection  |