The MultimediaCard™ (MMC) is a low cost data
storage and communication medium implemented as a
hardware card with a simple control unit and a compact,
easy-to-implement interface that is designed to cover a
wide variety of applications. MMC communication is
based on an advanced 7-pin serial bus designed to
operate in a low voltage range at medium speed. Secure
Digital Card (SD) is an evolution of the MMC with an
additional two pins in the form factor that is specifically
designed to meet the security, capacity, performance, and
environmental requirements inherent in new audio and
video consumer electronic devices. The physical form
factor, pin assignment, and data transfer protocol are
compatible with the MMC. The SD is composed of a
memory card and an I/O card. The I/O card combines
high-speed data input/output with low-power consumption for mobile electronic devices.