MultiMediaCard Technology

MultiMediaCard (MMC) is a low cost data storage and communication media, and is defined by the MultiMediaCard System Specification

The MMC specification is published by the MultiMediaCard Association.

Communication is based on a 7-pin serial bus designed to operate in a low voltage range (2.0 - 3.6V). The MultiMediaCard specification defines a communication protocol referred to as MMC mode (0-20MHz). In addition, for compatibility with existing controllers, MultiMediaCards may offer an alternative communication protocol which is based on the SPI standard (0-5MHz).


The following features of the MultiMediaCard System Specification are not provided in the Symbian platform MultiMediaCard controller:

  • Stream read and write operations are not supported.

  • SPI bus mode is not supported.

  • The MultiMediaCard System Specification includes a feature where a MultiMediaCard can be put into a disconnected state. This can be performed on a card which is currently in the programming state, i.e. writing data to the disk. To place that card into the disconnected state involves placing another card into the transfer state, which means giving the other card the current data transfer focus. A disconnected card will not terminate the programming operation and, if re-selected, moves back to the programming state. The Symbian platform MultiMediaCard controller does not support this mode of operation even if the underlying hardware interface does.