50.12.35 SDMMC Capabilities 1 Register

This field indicates the multiplier factor between the Base Clock (BASECLK) used for the Divided Clock Mode and the Multiplied Clock (MULTCLK) used for the Programmable Clock mode (see SDMMC_CCR).

Reading this field to 0 means that the Programmable Clock mode is not supported.

This field selects the retuning method and limits the maximum data length.

There are two retuning timings: Retuning Request (RTREQ) controlled by the SDMMC, and expiration of a Retuning timer controlled by the user. By receiving either timing, the user executes the retuning procedure just before a next command issue.

The maximum data length per read/write command is restricted so that retuning procedures can be inserted during data transfers.

Retuning Mode 1:

The SDMMC does not have any internal logic to detect when retuning needs to be performed. In this case, the user should maintain all retuning timings by using the Retuning Timer. To enable inserting the retuning procedure during data transfers, the data length per Read/Write command must be limited to 4 Mbytes.

Retuning Mode 2:

The SDMMC has the capability to indicate the retuning timing by Retuning Request (RTREQ) during data transfers. Then the data length per Read/Write command must be limited to 4 Mbytes.

During nondata transfer, retuning timing is determined by either Retuning Request or Retuning Timer. If Retuning Request is used, Retuning Timer should be disabled.

Retuning Mode 3:

The SDMMC has the capability to take care of the retuning during data transfer (Auto Retuning). Retuning Request is not generated during data transfers and there is no limitation to data length per Read/Write command.

During nondata transfer, retuning timing is determined either by Retuning Request or Retuning Timer. If Retuning Request is used, Retuning Timer should be disabled.

If this bit is set to 1, the SDMMC requires tuning to operate SDR50 (tuning is always required to operate SDR104).

This field indicates an initial value of the Retuning Timer for Retuning Mode (RTMOD) 1 to 3. Reading this field at 0 means that the Retuning Timer is disabled. The Retuning Timer initial value ranges from 0 to 1024 seconds.

t_TIMER = 2^{(TCNTRT – 1)}Seconds