confusion regarding the CMD19 and CMD21 in eMMC/SD card spec

[Philip Rakity]

Different committee's --- Different standards.

There is no issue with overlap.  


On Sep 15, 2011, at 4:58 AM, Girish K S wrote:

> Dear all,
>             The eMMC 4.5 specification mentions that the CMD21 in
> class 2 is a SEND_TUNING BLOCK command. where as the SD card
> specification
> in the given link says CMD19 in class 2 is the SEND_TUNING_BLOCK
> http://www.scribd.com/doc/50685191/53/Figure-4-8-Send-Tuning-Block-Command.
> Also the implementation in the drivers/mmc/host/sdhci.c uses the CMD19
> as the SEND_TUNING_BLOCK.
> Can anybody clarify why there is overlapping in this command number.
> May be my understand is wrong.
> 
> In the MMC spec the CMD19 is BUS_TEST_W in class 0 and CMD21 is
> reserved till eMMC 4.41 version.
> But in the SD specification (given link) CMD19 is SEND_TUNING_BLOCK
> and CMD21 is reserved.
> 
> Thanks and regards
> Girish K S
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