MMC/SD

[Brian]

Will the MMC drivers and schematic work for SD, or is a different setup?
thanks.

[ckielstra]

[Brian]

like this one
http://www.microchipc.com/sourcecode/#mmc

i dont care about formatting just want to be able to put data in address (x) similar to the eeprom setup. just need alot more space than eeprom.

http://www.sandisk.com/Assets/File/OEM/Manuals/SD_Physical_specsv101.pdf

according to this it appears it can. but someone may of done it and can let me know if it worked or anything that needs to be fiddled with to make it work..

and of course i will use 18f series with enough ram.

thanks again.

[ckielstra]

Search this forum and you will find some more MMC drivers. For example there is at least one MMC driver in the Code section of the forum and I remember a thread where there was a reference to a commercial library that supports several types of memory cards including SD cards.

Physically the SD cards differ from MMC cards in that they are a little bit thicker and have a few more I/O pins. Buy a connector that accepts SD and it will (almost) always accept MMC too, the other way around doesn't work. Check the SD card specifications for how to connect all pins, this is backwards compatible to MMC.

When accessing the cards in SPI mode the SD and MMC cards are quiet similar, I haven't checked out all the details but I think the largest difference is in the start-up sequence.

For storing data the MMC cards have a small advantage over SD cards because they are a bit cheaper and have more usable memory space (no licence costs and memory waste for the 'secure' features).
Another reason why you will find more MMC implementations is that the MMC early specifications used to be available at no costs and can still be found on the internet. For the SD card specifications you had to become a member of the SD group and pay a lot of money. Things have changed a bit the last couple of years, MMC and SD specifications have to be paid for now.

[asmallri]

The SD card has additional inputs that are used to support the native mode interface. These are not required for SPI mode however these additional pins must be pulled high (have pullup resistors fitted). Having said that, I used the standard MMC cct (as per your link) when I was developing my SD interface and left the unused inputs floating - this was because I was using an MMC connector on the prototype which did not include the additional pins.

SD cards can be read with MMC code (I have tested about 10 different brands of SD card without problem) but should ideally have a trivial change for the initialization. I found it easy to dermine which type of card (MMC or SD) was installed by issuing a SD specific command, if it returned without error it was an SD card, otherwise it was an MMC card.
_________________
Regards, Andrew

http://www.brushelectronics.com/software
Home of Ethernet, SD card and Encrypted Serial Bootloaders for PICs!!

[Brian]

Thanks Andrew that's what i wanted to know before i commited to my order and i have sd card on hand and didnt want to hunt for a mmc one. thnaks again.

[Brian]

oops thanks ckielstra for the info.