====== SD Host Controller ======

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|desc=Introduce the SD host controller (<wrap abbr>SDHC</wrap>) specified in SD specification.}}

<wrap abbr>SDHC</wrap> is the __standard__ controller specified by 
[[https://www.sdcard.org/developers/sd-standard-overview/host-controllers/|SD Association]] 
to manage SD Cards (SD Memory and SDIO).

<wrap abbr>SDHC</wrap> has been extended in connection with the Physical Layer functions extension.
Major improvement aimed increase of data transfer rate by supporting __higher SD 
bus speed modes__ and improvement of __Direct Memory Access (DMA)__.

  * SD Host Ver.2 supported **ADMA2** that can handle scattered paging data in system memory (scatter gather DMA).
  * SD Host Ver.3 supported **UHS-I** bus modes.
  * SD Host Ver.4 supported **UHS-II** bus modes, **ADMA3** ((note:>ADMA3 can execute __multiple of ADMA2 data transfers__ without intervention of Host Driver by Descriptor programing.
)) and **64-bit** system memory addressing.

===== Features List =====
<datatables>
^  Feature                                                                                                                       |^  Version                                                                                                                                                                 |||||
^ Description                                                                    ^ Key Component                                  ^ 2.00                             ^ 3.00                             ^ 4.00                             ^ 4.10                             ^ 4.20                             ^
| ADMA2 16-bit Data Length                                                       | ADMA2 descriptor                               | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| ADMA2 26-bit Data Length                                                       | ADMA2 descriptor                               | -                                | -                                | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| Re-define <wrap reg>SDMA_R</wrap> to 32-bit <wrap reg>Block Count</wrap>       | <wrap reg>SDMA_R</wrap>  ''000h''              | -                                | -                                | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| PLL control                                                                    | <wrap reg>Clock Control</wrap> ''02Ch''        | -                                | -                                | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| 10-bit divided clock mode                                                      | <wrap reg>Clock Control</wrap> ''02Ch''        | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| Programmable clock mode                                                        | <wrap reg>Clock Control</wrap> ''02Ch''        | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| Clock generator select (__Programmable clock mode__ / __Divided clock mode__)  | <wrap reg>Clock Control</wrap> ''02Ch''        | -                                | {{fa>check-circle?color=green}}  | -                                | -                                | -                                |
| Auto CMD12                                                                     | <wrap reg>Transfer Mode</wrap> ''00Ch''        | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| [[#auto_cmd23|Auto CMD23]]                                                     | <wrap reg>Transfer Mode</wrap> ''00Ch''        | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| Auto CMD auto select                                                           | <wrap reg>Transfer Mode</wrap> ''00Ch''        | -                                | -                                | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
| Response error check                                                           | <wrap reg>Transfer Mode</wrap> ''00Ch [8:6]''  | -                                | -                                | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  | {{fa>check-circle?color=green}}  |
</datatables>

==== Auto CMD23 ====

  * 32-bit block count value for ''CMD23'' is set to <wrap reg>SDMA</wrap>. ((:sdhc420-p43))

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===== Further Reading =====
  * //[[https://www.sdcard.org/developers/sd-standard-overview/host-controllers/]]//
  * //[[https://www.sdcard.org/downloads/pls/]]//