Make the following connections with the attached
device
Add a series resistor 0Ω
for MMC0_CLK signal as close to the processor as possible to dampen the
reflections (MMC0_CLK signal is used/looped back internally on read
transactions, and the series resistor is needed to eliminates possible
signal reflections, which can cause false clock transitions. Use series
resistor value of 0Ω initially and adjust to match the PCB trace
impedance as required)
- Connect an external
pulldown for MMC0_CLK signal (close to eMMC device). (To prevent the
eMMC device inputs from floating until software initializes the host
controller and processor IOs associated with MMC0 and the clock is
stopped or paused in a low logic and the pulldown option is
consistent with the logic state)
- Connect the external pullup
for the data line MMC0_DAT0 close to eMMC device (To prevent the eMMC device
inputs from floating until software initializes the host controller and
processor IOs).
- Provision for
external pullups is optional for DAT1-7. (The eMMC device (as long
as the eMMC device is compliant to the eMMC standard) has the
pullups enabled for data signals MMC0_DAT1-7. The eMMC device turns
off the MMC0_DAT1-3 pulls when entering 4-bit mode and MMC0_DAT1-7
pulls when entering 8-bit mode. The eMMC host software turns on the
respective DAT pulls when the software changes the mode)
- Connect the pullup (10kΩ or
47kΩ) for MMC0_CMD signal and pulldown with test point (optional) for DS
signal (close to eMMC device)