Cyclone® V Hard Processor System Technical Reference Manual
A.4.4.1.1. Default Settings of the SD/MMC Controller
|   Parameter  |  
         Default  |  
         Register Value  |  
      |
|---|---|---|---|
|   Card type  |  
         1 bit  |  
         The card type register (ctype) in the SD/MMC controller registers (sdmmc) = 0x0  |  
      |
|   Bus mode  |  
         —  |  
       SD/MMC71 | |
|   Timeout  |  
         Maximum  |  
         The timeout register (tmout) = 0xFFFFFFFF  |  
      |
|   FIFO threshold RX watermark level  |  
         1  |  
         The RX watermark level field (rx_wmark) of the FIFO threshold watermark register (fifoth) = 0x1  |  
      |
|   Clock source  |  
         0  |  
         The clock source register (clksrc) = 0x0  |  
      |
|   Block size  |  
         512  |  
         The block size register (blksiz) = 0x200  |  
      |
|   Clock divider  |  
         Identification mode  |  
         32  |  
         The clock divider register (clkdiv)= 0x10 (2*16=32)  |  
      
|   Data transfer mode  |  
         Bypass  |  
         The clock divider register (clkdiv)= 0x00  |  
      |
| External Device Power enable | Disabled (Power Off) |   The power_enable bit in the pwren register is programmed to 0x0 out of reset, meaning the sdmmc_pwren signal is not active and does not do anything at boot time. A pull-up should be attached to the sdmmc_pwren pin for proper functionality. 
         Note: If the SD/MMC controller is used as the boot source, then power to the corresponding SD card must be supplied from a power controller on the board. After boot has completed and the SD/MMC controller has been fully configured, the sdmmc_pwren signal can be used to turn on and off the SD card through the pwren register. 
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