Altera Cyclone V Device Handbook page 708

11-30
Power-On Reset Sequence
Figure 11-11: SD/MMC Controller Initialization Sequence
Power-On Reset Sequence
Software must perform the following steps after the power-on-reset:
1. Before enabling power to the card, confirm that the voltage setting to the voltage regulator is correct.
2. Enable power to the card by setting the power enable bit (power_enable) in the power enable register
(pwren) to 1. Wait for the power ramp-up time before proceeding to the next step.
3. Set the interrupt masks by resetting the appropriate bits to 0 in the intmask register.
4. Set the int_enable bit of the ctrl register to 1.
Note: Altera recommends that you write 0xFFFFFFFF to the rintsts register to clear any pending
interrupts before setting the int_enable bit to 1.
5. Discover the card stack according to the card type. For discovery, you must restrict the clock frequency
to 400 kHz in accordance with SD/MMC/CE-ATA standards. For more information, refer to Enumerated
Card Stack.
6. Set the clock source assignments. Set the card frequency using the clkdiv and clksrc registers of the
controller. For more information, refer to Clock Setup.
7. The following common registers and fields can be set during initialization process:
Altera Corporation
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Assert Active-Low Reset
Enable Power to Card
Set Interrupt Masks
Enumerate Card Stack
Set the Clock Source Assignments
Set Other Controller Registers
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SD/MMC Controller
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