For proper SDFM operation, use the
following GPIO input qualification. Other GPIO qualifications are not supported.
- GPIO Input qualification is
ASYNC, make sure to check the SDFM Electrical Data and Timing (Using ASYNC)
requirement is met and be aware of the following caution message. SDFM Input
Qualification feature is used to provide protection against random noise
glitches.
CAUTION: The SDFM clock
inputs (SDFMy_CLKy pins) directly clock the SDFM module. Any glitches or ringing
noise on these inputs can corrupt the SDFM module operation. Special precautions
must be taken on these signals to make sure of a clean and noise-free signal that
meets SDFM timing requirements. Precautions such as series termination for ringing
due to any impedance mismatch of the clock driver and spacing of traces from other
noisy signals are recommended.
Note:
The SDFM module expects SDFMy-Dx
to change on the falling edge of SDFMy_CLKx and strobes for SDFMy-Dx on the
rising edge. But some SD-modulators in the market change SDFMy-Dx on the rising
edge and expect SDFM to strobe for data on the falling edge. In such cases, the
GPIO inversion feature (GPxINV) is used on SDFMy-CLKx pin to change polarity and
make it compatible with the SDFM.
See the General-Purpose Input/Output (GPIO) chapter for more details on GPIO mux and settings.