Discussion around product based on ARM Cortex M3 core.

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Joined: Thu Jan 15, 2015 4:41 am


Thu Oct 08, 2015 5:34 am

I am trying to use the SAM3S-EK2 SD-CARD Read.

I have been programming using SD / MMC / SDIO Card FatFs Example.
I'm wondering some questions.


I try as much as possible to read the data from the SD card to a faster output SPI (DMA enabled).

As it stated in the data sheet below.
1. "Card Clock Rate Up to Master Clock Divided by 2"
2. "High Speed ​​Mode Support"

Q1. I thought High Speed ​​mode is supported by 50MHz, if the best clock of the card 'MCK / 2' as once conditions, the maximum possible clock going to a 64MHz / 2 32MHz?
Is there any way to use up to 50MHz?
Sample the "CHIP_FREQ_CPU_MAX = (64000000UL)" There is this defined as the maximum clock? Is there any further increase is?

Q2. Another example in the "HSMCI_SR_DMADONE" may be disabled, "HSMCI_MR_PDCMODE" is enabled.
Is the PDC and DMA is the difference? You are the other two?

Q3. What is the fastest method possible to transmit data to the SPI's attempts to output files in the SD CARD?

Please help.
Thank you !

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