UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
285 of 362
NXP Semiconductors
UM10208
Chapter 23: LPC2800 SD/MMC
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:
•
MCLK: One bit is transferred on each of the command and data lines with each clock
cycle. The clock frequency can be up to 20 MHz for a multimedia card, or 25 MHz for
a secure digital memory card.
•
MCMD: A bidirectional command channel that initializes a card and transfers
commands. CMD has two operational modes:
- Open-drain for initialization
- Push-pull for command transfer.
MD0: A bidirectional data channel, operating in push-pull mode.
4.2 Secure Digital memory card
shows the Secure Digital memory card connection.
4.2.1 Secure Digital memory card bus signals
The following signals are used on the Secure Digital memory card bus:
•
MCLK Host to card clock signal
•
MCMD Bidirectional command/response signal
Fig 31. Multimedia card system
MULTIMEDIA CARD BUS
POWER
SUPPLY
MULTIMEDIA
CARD
INTERFACE
MULTIMEDIA CARD STACK
CARD
CARD
CARD
Fig 32. Secure Digital memory card connection
SECURE
DIGITAL
MEMORY CARD
CONTROLLER
SECURE
DIGITAL
MEMORY CARD
MCLK
MCMD
MD[3:0]