User Guide

Figure 99 MMC interface

The basic multimedia card concept is based on the following communication signals CLK, CMD and DAT. With

each cycle of the CLK signal one bit transfer on the DAT and CMD line is done. The maximum CLK frequency is

20MHz (specified in multimedia card specification). Maximum used CLK frequency at the time is 16MHz. CMD is

a bi-directional command channel used for card initialization and data transfer commands. CMD signal has two

operational modes open-drain and push-pull mode. Open-drain mode is used for card initialization and push-

pull mode for fast command transfer. CMD commands are sent by the host and CMD responses are sent by the

card. DAT is a bi-directional data channel, which operates at push-pull mode.

The detection of RS MMC card removal/insertion is done via RS MMC cover switch. Removing RS MMC while writing

to RS MMC may corrupt data in RS MMC. RS MMC cover switch gives an interrupt to the SW while the cover is

opened or closed. After RS MMC cover lid opening (RS MMC SW signal is connected to GND via cover switch) the

SW power down the RS MMC card and switches off the RS MMC power supply (VSIM2). When the RS MMC cover

lid is closed (RS MMC SW signal is internally connected in Helen3 to 1.8V) the card should be identified if card

exists.