MultiMediaCardTM
4.2 Pin Assignments in SPI Mode
Table 4- 2 SPI Pad Definition
Pin No.
Name
CS
DI
Vss
Vcc
SCLK
Vss2
DO
Type*1
I
I
S
S
I
S
O/PP
Description
Chip Select
Data In
Ground
Power supply
Clock
1
2
3
4
5
6
7
Ground
Data out
Note : 1. S: power supply; I: input; O: output; PP: push-pull; OD: open-drain; NC: No connection or VIH
4.3 MultiMediaCard Bus Topology
The MultiMediaCard bus has three communication lines and four supply lines:
- CMD: Command is a bi-directional signal. Host and card drivers are operating in two modes, open
drain and push pull.
- DAT: Data is a bi-directional signal. Host and card drivers are operating in push pull mode.
- CLK: Clock is a host to card signal. CLK operates in push pull mode.
- VDD: VDD is the power supply line for all cards.
- VSS[1:2]: VSS are two ground lines.
Figure 4-2 Bus Circuitry Diagram
The ROD is switched on and off by the host synchronously to the open-drain and push-pull mode
transitions. RDAT and RCMD are pull-up resistors protecting the CMD and the DAT line against bus
floating when no card is inserted or when all card drivers are in a hi-impedance mode. A constant
current source can replace the ROD by achieving a better performance (constant slopes for the signal
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