tis true. The issue I raise though is that the DM355's SD/MMC module itself
claims an internal upper frequency range of 100MHz. Check out Page 12 of:
" MS320DM35x Digital Media
System-on-Chip (DMSoC)
Multimedia Card (MMC)/Secure Digital (SD)
(SDIO) Card Controller
Reference Guide"
( SPRUEE2C)
Here's a snip from it
"The MMC/SD controller has two clocks, the function clock and the memory clock
(Figure 4).
The function clock determines the operational frequency of the MMC/SD
controller and is the input clock
to the MMC/SD controller on the device. The MMC/SD controller is capable of
operating with a function
clock up to 100 MHz."
Problem is, if you are running your part at 270 MHz, the input clock is 135 MHz.
________________________________________
From: Saxena, Anshuman [[email protected]]
Sent: Thursday, July 22, 2010 12:30 AM
To: Paul Stuart; '[email protected]'
Subject: RE: Dm355-270 SD/MMC Module Freq
Stuart,
I was mentioning about the CLKRT register in MMC/SD controller. That can be
programmed to send out a lower clock to SD card, to meet the specification of
less than 50MHz for SDHC cards.
Regards,
Anshuman
-----Original Message-----
From: Paul Stuart [mailto:[email protected]]
Sent: Thursday, July 22, 2010 10:16 AM
To: Saxena, Anshuman; '[email protected]'
Subject: RE: Dm355-270 SD/MMC Module Freq
Unfortunately it is a fixed divide-by-four, so the module frequency is strictly
coupled to the system clock.
________________________________________
From: Saxena, Anshuman [[email protected]]
Sent: Wednesday, July 21, 2010 6:55 PM
To: Paul Stuart; '[email protected]'
Subject: Re: Dm355-270 SD/MMC Module Freq
Hi,
If I remember correctly, there is an internal divider in the MMC/SD module
which can control the clock going into the module. I have to double check
though.
We had used DM355-270 version and had it working with slower SD cards at 25-30
MHz clock also. So I assume your use case should be covered.
Regards,
Anshuman
----- Original Message -----
From: davinci-linux-open-source-bounces+anshuman=ti....@linux.davincidsp.com
<davinci-linux-open-source-bounces+anshuman=ti....@linux.davincidsp.com>
To: [email protected]
<[email protected]>
Sent: Thu Jul 22 03:22:37 2010
Subject: Dm355-270 SD/MMC Module Freq
Hi There,
Does anyone know if the DM355-270 can run at full speed and have reliable
SD/MMC module behavior?
We are using the 270 MHz variety of the DM355, clocked up to 270MHz. Now, the
SD/MMC module claims that it only supports a module clock speed up to 100MHz,
but running at 270 MHz produces a module's clock of 135 MHz.
Since the sysclk2 divider is a fixed, to even get close to spec (108MHz) one
would need to clock the ARM down to 216MHz... and start asking why we paid more
for the 270 MHz part :)
I see mostly good behavior on SDHC cards when we are over clocking the module
at 135MHz, but get cards every now and again that throw buffer IO errors on
data read timeouts. Anyone vouch for 135 MHz module clock working with a
variety of SDHC cards?
Thanks,
Paul
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