TMS320C6748: FXS Support for TMS320C6748

Hi Gui Kang,

I'm not sure what you mean by FXS ports. Are you referring to VoIP? Is there a device that you want to connect to the SPI pins? Can you provide that part number?

There are two SPI interfaces: SPI0 and SPI1. SPI0 has 6 CS pins, SPI1 has 8 CS pins.
You can configure either SPI interface to use those CS pins during a transfer.

With one SPI interface, you can select one or multiple chip selects with the CLK, MOSI, and MISO connections are shared for all the chip selects. So SPI could be a master to multiple chip selects, sending them the same data. Or it can reconfigure the SPIDAT1 register to change which chip select(s) it is accessing and then send different data (time sliced).

A single SPI interface cannot, however, transfer different information simultaneously to  multiple chip selects. There is only one set of CLK, MOSI, and MISO pins for each SPI interface that must be shared with the multiple CS pins available to that SPI interface.

Refer to Technical Reference Manual (SPRUH79C) Section 28.3.13 SPI Data Register 1 (SPIDAT1) bits 23-16 CSNR[n] Chip select number. The CSNR field defines the state of the SPIx_SCS[n] pins during a master data transfer.

Note that there are other registers that must be programmed. Refer to SPRUH79C Section 28.2.19 Initialization for more.

Regards,
Mark