Data Sampling
clk
cmd, dat[x:0]
(Host
Card)
®
cmd, dat[x:0]
(Host
Card)
¬
tMOS
tMOH
Valid OUT
tMIS
tCP
tC2
tC1
tMiH
Valid IN
Functional Description
18.3.12 Output Signals Generation
The MMC/SD/SDIO output signals can be driven on either falling edge or rising edge depending on the
SD_HCTL[2] HSPE bit. This feature allows to reach better timing performance, and thus to increase data
transfer frequency.
18.3.12.1 Generation on Falling Edge of MMC Clock
The controller is by default in this mode to maximize hold timings. In this case, SD_HCTL[2] HSPE bit is
cleared to 0.
shows the output signals of the module when generating from the falling edge of the MMC
clock.
Figure 18-29. Output Driven on Falling Edge
18.3.12.2 Generation on Rising Edge of MMC Clock
This mode increases setup timings and allows reaching higher bus frequency. This feature is activated by
setting SD_HCTL[2] HSPE bit to 1. The controller shall be set in this mode to support SDR transfers.
NOTE:
Do not use this feature in Dual Data Rate mode (when SD_CON[19] DDR is set to 1).
shows the output signals of the module when generating from the rising edge of the MMC
clock.
3378
Multimedia Card (MMC)
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated