UM10211 - Standard ICs

NXP Semiconductors
UM10211
Chapter 18: LPC2300 SD_MMC
POWER
SUPPLY
MULTIMEDIA
CARD
INTERFACE
MULTIMEDIA CARD BUS
CARD CARD CARD
MULTIMEDIA CARD STACK
Fig 71. 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
4.2 Secure digital memory card
Figure 18–72 shows the secure digital memory card connection.
SECURE
DIGITAL
MEMORY CARD
CONTROLLER
CLK
CMD
D[3:0]
SECURE
DIGITAL
MEMORY CARD
Fig 72. 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:
• CLK Host to card clock signal
UM10211_1
© NXP B.V. 2007. All rights reserved.
User manual Rev. 01 — 27 March 2007 392 of 613