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Source code


Name: sd_card_controller
Created: Sep 1, 2013
Updated: Sep 10, 2013
SVN Updated: Sep 10, 2013

Other project properties

Category: Communication controller
Language: Verilog
Development status: Beta
Additional info: Design done , FPGA proven , Specification done
WishBone Compliant: Yes
License: LGPL


The Wishbone SD Card Controller IP Core is MMC/SD communication controller designed to be
used in a System-on-Chip. The IP core provides a simple interface for any CPU with Wishbone
bus. The communication between the MMC/SD card controller and MMC/SD card is performed
according to the MMC/SD protocol.


This core is based on the "sd card controller" project from
but has been largely rewritten. A lot of effort has been put
forth to make the core more generic and easily usable
with OSs like Linux.
- data transfer commands are not fixed
- data transfer block size is configurable
- multiple block transfer support
- R2 responses (136 bit) support


The MMC/SD card controller provides following features:
- 1- or 4-bit MMC/SD mode (does not support SPI mode),
- 32-bit Wishbone interface,
- DMA engine for data transfers,
- Interrupt generation on completion of data and command transactions,
- Configurable data transfer block size,
- Support for any command code (including multiple data block tranfser),
- Support for R1, R1b, R2(136-bit), R3, R6 and R7 responses.


The documentation is located in the doc/ directory of the svn repository.


A sample ORPSoC project that make use of this core is located at:
The project is based on de0_nano board with custom made expansion board
with SD Card connector.
There is also u-boot project port for this board located at:
This u-boot project contains driver for Wishbone SD Card Controller IP Core
and can be configured for de0_nano board (with custom made expansion board).
Also in the plan is the driver for Linux. The initial work can be found at:
https://github.com/mczerski/linux - de0_nano branch
the driver is named ocsdc and is located in drivers/mmc/host directory.


- top level testbench cleanup (sd_controller_top_tb.sv)
- rx/tx fifo treshold to do block transfers rather than many single word transfers
- maybe one fifo rather than two fifos (rx and tx) would suffice since the transfer
between card and controller is always half-duplex
- read only and card detect signals support
- timeout watchdog for data transfers