Make the following connections with the attached
device
-
Add a series resistor 0Ω for MMC0_CLK signal as
close to the processor clock output pin as
possible to minimize the reflections (MMC0_CLK
signal is used/looped back internally on read
transactions, and the series resistor minimizes
possible signal reflections, which can cause false
clock transitions. Use series resistor value of 0Ω
initially and adjust the value to match the PCB
trace impedance as required)
- Connect an external pulldown for MMC0_CLK signal
(close to eMMC device clock input pin). (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)