Nxp Semiconductors UM10237 ユーザーズマニュアル

UM10237_2

© NXP B.V. 2008. All rights reserved.

There is one additional signal needed in the interface, a power control line MCIPWR, but it 
can be sourced from any GPIO signal.

The MCI may be used as a multimedia card bus host (see 

) or a secure digital memory card bus host (see 

). Up to 4 multimedia cards (depending on board loading) or a single secure 

digital memory card may be connected.

 shows the multimedia card system.

 

Multimedia cards are grouped into three types according to their function:

Read Only Memory (ROM) cards, containing pre-programmed data

Read/Write (R/W) cards, used for mass storage

Input/Output (I/O) cards, used for communication

The multimedia card system transfers commands and data using three signal lines:

CLK: One bit is transferred on both command and data lines with each clock cycle. 
The clock frequency varies between 0 MHz and 20 MHz (for a multimedia card) or 
0 MHz and 25 MHz (for a secure digital memory card).

CMD: Bidirectional command channel that initializes a card and transfers commands. 
CMD has two operational modes: 

– Open-drain for initialization

– Push-pull for command transfer

DAT: Bidirectional data channel, operating in push-pull mode

 shows the secure digital memory card connection.

MULTIMEDIA CARD BUS

POWER
SUPPLY

MULTIMEDIA

CARD

INTERFACE

MULTIMEDIA CARD STACK

CARD

CARD

CARD