7.3.2.2.2.1 MMC1 Signals Used for SD Card Interface
(Recommended)
The recommendation is to add a
series resistor (0Ω) for MMC1_CLK (close to processor clock output pin to
control possible signal reflections). A pulldown (10kΩ) is recommended for
MMC1_CLK near to the attached device input to hold the clock in low state (there
are cases where the clock is stopped or paused in a low logic state and the
pulldown option is consistent with this logic state) until the host configures
the signal as clock.
The recommendations is to add
external pullups (47kΩ) for the SD card data signals (MMC1_DAT[3:0]) and CMD
signal (MMC1_CMD) to prevent the attached device inputs from floating until the
host software drives the interface signals. The recommendation is to connect the
SD card interface signals pullup to dual-voltage IO supply for IO group (MMC1 =
VDDSHV5) supply rail.
The recommendation is to add
external pullups (10kΩ or 47kΩ) for the MMC1_SDCD and MMC1_SDWP signals
connected to the VDDSHV0 supply rail (close to attached device (SD card
socket)).
SD Card Detect (SDCD) input to the processor connects directly to ground when
the SD card is inserted. A series resistor (100Ω) to limit the current in case
the IO is programmed as output unexpectedly is recommended.