[Arm-netbook] "[EOMA68] RFC: ADDITION OF SD/MMC TO STANDARD."

[Luke Kenneth Casson Leighton]

On Mon, Dec 23, 2013 at 10:08 PM, Christopher Thomas
<christopher at firemothindustries.com> wrote:
>
>
> Sent from my iPhone
>
>> On Dec 23, 2013, at 3:48 PM, Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:
>>
>> i'm giving serious consideration, even at this late phase, to adding
>> SD/MMC to EOMA68 by way of the GPIO pins as a multiplexing option.
>> this would not have any impact on the EOMA68-A20 CPU Card: in fact,
>> the only reason this can be considered at all is because the pins
>> *happen* to be multiplexed as SD/MMC and GPIO *anyway*.
>>
>> does anyone have any objections, and/or can think of any gotchas which
>> would prevent SD/MMC from being added as a non-optional multiplexed
>> option to EOMA-68?
>>
>
> How many of the 8 GPIO would essentially be used? (I presume 6?)

 yes, 6.  it's no change - literally - of the EOMA68-A20 CPU Card.
the pinouts happen already to be multiplexed to SD/MMC (just at
present in "non-EOMA68-compliant" mode).  the change would be "it is
now mandatory that the following pins be multiplexed on GPIO [1]:

GPIO-0: SD0-D3
GPIO-1: SD0-D2
GPIO-4: SD0-CMD
GPIO-5: SD0-CLK
GPIO-6: SD0-D0
GPIO-7: SD0-D1

l.

[1] from http://rhombus-tech.net/allwinner_a10/orders/ - the section
on "Features".  these pins were originally selected because they have
a secondary multiplex functional mapping to JTAG, but also because of
the *tertiary* multiplex functional mapping to SD/MMC.