The recommendation is to make the
following connections:
- The recommendation is to add
a series resistor (0Ω) for MMC0_CLK signal close to processor clock output
pin (The series resistor is recommended to control possible signal
reflections, which can cause false clock transitions). The recommendation is
to use 0Ω initially and adjust to match the PCB trace impedance.
- An external pulldown (10kΩ)
(close to attached eMMC device clock input pin) is recommended for MMC0_CLK
near to the attached device clock input pin 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 recommendation is to
connect external pullup (47kΩ) for MMC0_DAT0 and MMC0_CMD signals (close to
eMMC device) to prevent the attached device inputs from floating until the
host software drives the interface signals.
- Pullup resistors are
optional (delete or DNI) for MMC0_DAT[7:1] signals since the
attached eMMC device (eMMC device compliant to the eMMC JEDEC
standard JESD84-B51) is required (expected) to turn on internal
pullups for the MMC0_DAT[7:1] signals until the host changes the bus
width to 4-bit or 8-bit mode. The host is expected to enable the
internal pullups and the eMMC device is expected to turn off the
internal pullups on MMC0_DAT[3:1] when changing to 4-bit mode. The
host is expected to enable the internal pullups and the eMMC device
is expected to turn off the internal pullups or MMC0_DAT[7:1] when
changing to 8-bit mode.
- The recommendation is to
connect a pulldown with test point (optional) for DS signal (close to the
eMMC device).