SPRUHM9H October 2014 – May 2024 TMS320F28075 , TMS320F28075-Q1 , TMS320F28076
The sample rate generator can produce a clock signal (CLKG) for use by the receiver, the transmitter, or both. Use of the sample rate generator to drive clocking is controlled by the clock mode bits (CLKRM and CLKXM) in the pin control register (PCR). When a clock mode bit is set to 1 (CLKRM = 1 for reception, CLKXM = 1 for transmission), the corresponding data clock (CLKR for reception, CLKX for transmission) is driven by the internal sample rate generator output clock (CLKG).
The effects of CLKRM = 1 and CLKXM = 1 on the McBSP are partially affected by the use of the digital loopback mode and the clock stop (SPI) mode, respectively, as described in Table 20-4. The digital loopback mode (described in Section 20.8.4) is selected with the DLB bit of SPCR1. The clock stop mode (described in Section 20.7.2) is selected with the CLKSTP bits of SPCR1.
When using the sample rate generator as a clock source, make sure the sample rate generator is enabled (GRST = 1).
Mode Bit Settings | Effect | |
---|---|---|
CLKRM = 1 | DLB =
0 (Digital loopback mode disabled) |
CLKR is an output pin driven by the sample rate generator output clock (CLKG). |
DLB =
1 (Digital loopback mode enabled) |
CLKR is an output pin driven by internal CLKX. The source for CLKX depends on the CLKXM bit. | |
CLKXM = 1 | CLKSTP = 00b or 01b (Clock stop (SPI) mode disabled) |
CLKX is an output pin driven by the sample rate generator output clock (CLKG). |
CLKSTP = 10b or 11b (Clock stop (SPI) mode enabled) |
The McBSP is a master in an SPI system. Internal CLKX drives internal CLKR and the shift clocks of any SPI-compliant slave devices in the system. CLKX is driven by the internal sample rate generator. |