Question: Under BSP mode, does C54x support 8-bit PCM mode? If yes, how to configure?

Answer: The BSP does not fully support 8-bit PCM mode. Besides that the BSP does not handle the Framing Bit, you cannot disable the receive channels hence some memory will be wasted. But you can disable the transmit channels by using the PCM bit. If this PCM bit and the transmit data bit 15 are set, the DX pin will be tri-stated for word length (FO/FE bits) number of CLKX.