版本 59658a5d064bcb902d5753da95ae155170a8b149
Changes from 59658a5d064bcb902d5753da95ae155170a8b149 to 580568b5cbd26086f23dac574f7b3d203a80757e
---
title: Secure digital input/output interface (SDIO)
categories: SDIO, STM32F4
...
Introduction
============
What is SDIO?
-----------------
- A SDIO (Secure Digital Input Output) card is an extension of the SD specification to cover I/O functions.
- Host devices that support SDIO can use the SD slot to support:
1. GPS receivers.
2. digital cameras.
3. RFID readers.
4. FM radio tuners.
5. TV tuners.
6. Wi-Fi.
7. Bluetooth.
Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface.
- SDIO cards support most of the memory commands of SD cards. SDIO cards can be structured as 8 logical cards, although currently, the typical way that an SDIO card uses this capability is to structure itself as one I/O card and one memory card.
.. image:: /sdio1.png
.. image:: /sdio2.png
Difference of SD/MMC/SDIO
--------------------------
Speed class rating
-------------------
SDIO bus topology
=================
.. image:: /Selection_015.png
.. image:: /Selection_016.png
Note: The SDIO will not send any data as long as the Busy signal is asserted (SDIO_D0 pulled
low).
.. image:: /Selection_017.png
.. image:: /Selection_018.png
.. image:: /Selection_019.png
SDIO functional description
============================
.. image:: /sdio_functional_description.png
圖說明：
- SDIO_D0預設是用來當作資料傳輸 , 而在初始化時 , host端可以設定其資料寬度。
- 當MMC連至bus時 , MMC可以支援只有1bit模式。
- 當SD/SD I/O連至bus時,data transfer可以由host端來設定是SDIO_D0(1bit mode) 或者是 SDIO_D[3:0](4bit mode)
而所有的data lines都是操作於push-pull mode.
SDIO_CMD has two operational modes:
- Open-drain for initialization (only for MMCV3.31 or previous)
- Push-pull for command transfer (SD/SD I/O card MMC4.2 use push-pull drivers also for
initialization)
SDIO_CK is the clock to the card:
- 在clock cycle 中 , 1 bit是用來切換command 或是 data lines.
- clock的頻率依照規格不同有所不同：
* between 0 and 20 MHz (for a MultiMediaCard V3.31).
* between 0 and 48 MHz for a MultiMediaCard V4.0/4.2).
* between 0 and 25 MHz (for an SD/SD I/O card).
- The SDIO uses two clock signals:
* SDIO adapter clock(SDIOCLK = 48MHz is coming from a specific output of PLL (PLL48CLK) ).
* APB2 bus clock(PCLK2).
NOTE: PCLK2 與 SDIO_CLK 之clock頻率必須遵循以下條件：
Frequency PCLK2 ≥ (3/8) * Frequency SDIO_CK ?????????????????
The signals shown in Table 149 are used on the MultiMediaCard/SD/SD I/O card bus
.. image:: /SDIO_IO_definitions.png
SDIO adapter
==============
block diagram of an SDIO adapter.
.. image:: /sdio_adapter.png
上圖中包含了五個子單元：
- Adapter register block
- Control unit
- Command path
- Data path
- Data FIFO
由圖中可以看出 , adapter registers 和 FIFO都是採用APB2 bus clock domain (PCLK2),
而control unit , command path , data path 則是採用SDIO adapter clock domain(SDIOCLK).
Q&A : WHY??????????????????????????????????????????????????????
上圖中之左側部份（Adapter registers and FIFO）：
Adapter registers 主要包含了所有SDIO的暫存器 , 而這些暫存器是用來配置一些參數,以用來實現SD協定中的時序,最終目的是用來實現SD卡的命令傳輸。
而FIFO則是為了實現與data path的傳輸。
而FIFO則是為了實現與data path的傳輸 , 而這兩個分別代表著對SD卡的兩種操作模式 , 一個是命令的傳輸 , 一個是資料的傳輸。
上圖中之右側
主要分為三個子單元 , Control Unit , Command Path and Data Path , Control Unit主要用來控制電源以及時鐘的控制 , 而這些控制是根據Adapter registers當中的暫存器來做配置 , 而Command Path連結SDIO_CMD , 他用來控制命令的傳輸 , 最後Data Path則是連結SDIO_D[7:0],控制資料的傳輸。
Reference
==========
- `Secure Digital wiki<http://en.wikipedia.org/wiki/Secure_Digital#SDIO>`_
- `SDIO接口介绍<http://en.wikipedia.org/wiki/Secure_Digital#SDIO>`_
- `Linux（open source）的 SD/MMC/SDIO 支援現況概要<http://www.jollen.org/blog/2007/01/open_source_sd_mmc_sdio.html>`_
- `SD/MMC/SDIO概念區分<http://bbs.ednchina.com/BLOG_ARTICLE_198217.HTM>`_
- `STM32 控制 SD 卡<http://www.360doc.com/content/12/0411/15/9707346_202767012.shtml>`_
- `STM32 + SDIO + FATFS 文件系统 直讀 SD 卡<http://ntn314.blog.163.com/blog/static/16174358420112263456948/>`_
- `零死角玩轉 stm32 - 高級篇之 SDIO（4bit + DMA、支持SDHC、帶協議分析）<http://www.eeboard.com/tutorials/%E9%9B%B6%E6%AD%BB%E8%A7%92%E7%8E%A9%E8%BD%ACstm32-%E9%AB%98%E7%BA%A7%E7%AF%87%E4%B9%8Bsdio%EF%BC%884bit-dma%E3%80%81%E6%94%AF%E6%8C%81sdhc%E3%80%81%E5%B8%A6%E5%8D%8F%E8%AE%AE%E5%88%86%E6%9E%90/>`_
