The PCM / the DSP MODE divided Mode-A and Mode-B were 2 modes. Some datasheets of different chips are called PCM mode; some are called DSP mode.
I2S mode is divided into three modes: standard i2s- standard mode (also become Philips standard), i2s- MSB-Left-justified mode, and i2s- MSB-Right-justified mode.
The specific data format and timing are described in detail in the following two articles
https://blog.csdn.net/azloong/article/details/6536855
https://blog.csdn.net/u011011827/article/details/99884868
https://blog.csdn.net/dfysy/article/details/6105437
https://blog.csdn.net/chuanzhilong/article/details/77435267
The picture below captures the datasheet of NXP's codec chip SGTL5000
