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).