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sd_card [2017/03/26 22:05] gongyu |
sd_card [2020/01/18 22:18] (当前版本) gongyu |
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| 行 9: | 行 9: | ||
| {{ ::sd_modes.gif |}} | {{ ::sd_modes.gif |}} | ||
| - | ====== SPI mode ====== | + | #### SPI模式 |
| In SPI mode, the DI/DO lines are unidirectional. That means: | In SPI mode, the DI/DO lines are unidirectional. That means: | ||
| 行 32: | 行 32: | ||
| {{ ::sd_fpgaonebit.gif |}} | {{ ::sd_fpgaonebit.gif |}} | ||
| - | ====== 协议 ====== | + | #### 协议 |
| SD cards work with a command/response scheme. For example, command "17" allows reading one sector (512 bytes) of the card memory. All communication is synchronous to a clock provided by the host (FPGA in our case). The clock should run below 400KHz at startup and can go faster after some card initialization. | SD cards work with a command/response scheme. For example, command "17" allows reading one sector (512 bytes) of the card memory. All communication is synchronous to a clock provided by the host (FPGA in our case). The clock should run below 400KHz at startup and can go faster after some card initialization. | ||
| 行 39: | 行 39: | ||
| <code verilog> | <code verilog> | ||
| - | |||
| // we use the Xylo-E FX2 FIFO2 as data source for "commanding" an SD card | // we use the Xylo-E FX2 FIFO2 as data source for "commanding" an SD card | ||
| // the SD card is used in one-bit SD mode | // the SD card is used in one-bit SD mode | ||
| 行 67: | 行 66: | ||
| * CMD8 "SEND_IF_COND", response expected | * CMD8 "SEND_IF_COND", response expected | ||
| - | ====== 相关资源 ====== | + | #### 相关资源 |
| - | + | * Seabright技术公司的[[http://wiki.seabright.co.nz/wiki/SdCardProtocol.html|SD卡的协议]] | |
| - | Seabright技术公司的[[http://wiki.seabright.co.nz/wiki/SdCardProtocol.html|SD卡的协议]] | + | * Wikipedia上[[http://en.wikipedia.org/wiki/Secure_Digital|关于SD卡的介绍]]. |
| - | Wikipedia上[[http://en.wikipedia.org/wiki/Secure_Digital|关于SD卡的介绍]]. | + | * SD联盟的最新[[https://members.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf|简化SD规范]] |
| - | SD联盟的最新[[https://members.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf|简化SD规范]] | + | |