ST7 too limited for MMC/SD use?

[stm2]

Posted on January 12, 2007 at 09:25

ST7 too limited for MMC/SD use?

[stm2]

Posted on January 12, 2007 at 09:25

Hi,

On a current design I've been working on we've put a

MMC/SD card slot on-board with a view to logging to it.

The limitation I'm up against is that the ST7 itself

wouldn't handle a 512K byte sector in it's own memory

so the aim was to use a eeprom memory chip to work as

an intermediary. However, because they're both on the

SPI bus does this mean that comms with the MMC card

would be 'reset' as a result of switching to the memory

(i.e. dropping the chip select line)?

Technically after erasing a sector then writing smaller

bits at a time should work as can you start writing anywhere

within the sector so not to over-write anything?

As anyone had any joy with such an approach?

The same is true of the USB. Using low-speed I should be

able to request and send data through the ST7 to a PC from

the card. As this will be done in smaller blocks then

I can't see a problem with this as I'd only be reading.

Regards,

Mark