Theory of Operation: Controller 3-37
A GPIO named "MMC_RESET" will be used to soft-reset the eMMC card. This will be an output from
CPLD ball C7. This ball is on output high out of reset. On power-up software should drive the pin low
for at least 5ms and then drive it high. After reset is driven high, software needs to wait 250ms before
sending command CMD0 (argument = 0). Refer to the sw code to see how to add delays with
MMC_CLK running for at least 74 clock cycles after any reset occurs. If not, the eMMC will fail to
initialize and will not open since the OMAP does not run the clock continuously, so waiting 250ms
with no clock running will not configure eMMC correctly.
Figure 3-23. Timing of power-up and initialization of eMMC
V
CCQ,min
V
CCQ,max
V
CCQ
V
CC,max
V
CC,min
Supply voltage
Power-up time Supply ramp-up time First CMD1 to card ready
Initialization sequence
CMD1 CMD1 CMD2CMD1
N
CC
N
CC
N
CC
Optional repetitions of CMD1
until the card is responding
with busy bit set
Initialization delay =
the longest of 1ms, 74 clock cycles,
the supply ramp-up time,
or the boot operation period.
Control logic
working
voltage range
Memory field
working
voltage range
To Next Page
Loading...
Need help?
General
