7.3.2.2.2.2 MMC2 Signals Used for SD Card
Interface
The recommendation is to add a
series resistor (0Ω) for MMC2_CLK (close to processor clock output pin to
control possible signal reflections). A pulldown (10kΩ) is recommended for
MMC2_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 (MMC2_DAT[3:0]) and CMD
signal (MMC2_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 (MMC2 =
VDDSHV6) supply rail.
For supporting SD card interface,
the recommendation is to connect MMC2_SDCD and MMC2_SDWP signals referenced
(power) to VDDSHV0. The recommendation is to add external pullups (10kΩ or
47kΩ) for the MMC2_SDCD and MMC2_SDWP signals connected to the same supply rail
that is connected to 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.