MMC/SD/SDIO2
mmc2_clkin
mmc2_clk
mmc2_dir_dat[2:0]
mmchs-005
mmc2_dir_cmd
mmc2_cmd
mmc2_dat[3:0]
Public Version
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MMC/SD/SDIO Environment
24.2.3.2 Basic MMC/SD/SDIO2 Pins With External Transceiver
shows the MMC/SD/SDIO2 host controller interface signals.
Figure 24-6. MMC/SD/SDIO2 Interface Signals
describes the MMC/SD/SDIO2 inputs/outputs.
Table 24-2. MMC/SD/SDIO2 I/O Description
Signal Name
I/O
Description
Reset Value
mmc2_clk
O
External clock for MMC/SD/SDIO card
0
mmc2_clkin
I
Input clock from MMC/SD/SDIO card
0
mmc2_cmd
I/O
Command signal
0
mmc2_dir_cmd
O
Direction control for mmc2_cmd signal case an external
0
transceiver is used (high when transmit, low when receive)
mmc2_dat[3:0]
I/O
Data signals
0
mmc2_dir_dat0
O
Direction control for mmc2_dat0 signal when an external
0
transceiver is used (high when transmit, low when receive)
mmc2_dir_dat1
O
Direction control for mmc2_dat1 and mmc2_dat3 signal when an
0
external transceiver is used (high when transmit, low when
receive)
mmc2_dir_dat2
O
Direction control for mmc2_dat2 signal when an external
0
transceiver is used (high when transmit, low when receive)
mmc2_dir_dat3
O
Direction control for mmc2_dat[7:4] signal when an external
0
transceiver is used (high when transmit, low when receive).
Unusable on the device because mmci_dat[7:4] are muxed with
other direction control signals. See
, System Control
Module for further details on the pin multiplexing.
24.2.3.3 MMC/SD/SDIO Protocol and Data Format
The bus protocol between the MMC/SD/SDIOi host controller and the card is message-based. Each
message is represented by one of the following parts:
Command: a command starts an operation. The command is transferred serially from the MMC/SD/SDIO
host controller to the card on the mmci_cmd line.
Response: a response is an answer to a command. The response is sent from the card to the
MMC/SD/SDIO host controller. It is transferred serially on the mmci_cmd line.
Data: data are transferred from the MMC/SD/SDIOi host controller to the card or from a card to the
MMC/SD/SDIO host controller using the DATA lines.
Busy: the mmci_dat0 signal is maintained low by the card as far as it is programming the data received.
3369
SWPU177N – December 2009 – Revised November 2010
MMC/SD/SDIO Card Interface
Copyright © 2009–2010, Texas Instruments Incorporated