Hi Oleg,
Many thanks for your reply.
I have double confirmed, that MMC Standard particularly says that MMC cards will communicate in 2 modes: Card Bus, And SPI.
Card Bus concept is used for high speed processors, which can communicate to the MMC Card through the MMC Card Controller (adapter). With this mode you can access the MMC with the CLK, CMD, DATA lines.
SPI Bus Concept is used for MMC Cards to be used with lower end processors (compared to PC processors) such as Motorola 68XX series and other microprocessors which includes MCS-51. They can communicate with the MMC card over the SPI Bus (CS, CLK, DI, DO), without the MMC Controller (adapter). This SPI Bus was specifically introduced for low-speed and very low end MMC interface. If you want I can mail you the MMC Specifications which mentions the points I mentioned above.
I had downloaded this PDF from the Internet, but I forgot the link. You can send me a request mail at my email address: mr_kiran@yahoo.com.

Thanks for your reply,
Mr. Kiran V. Sutar.