Special Considerations
Setup and Use of the Multimedia Card/Secure Digital Host Controller Application Note, Rev. 0
10
Freescale Semiconductor
Figure 3. SD_CLK (1) and SD_DAT [0] (2) Multiple Block Read
Both screenshots were captured using a low driving strength. If the driving strength (DS_SLOW bits) is
set to the maximum drive strength, it causes overshoot on the SD_CLK signal.
4.3.3
Stream Write and Read
The Stream Mode is not supported in any of the three processors.
5
Special Considerations
The MMC/SD module varies in speed during the data transfer mode.
Table 3
and
Table 4
describe the
various speeds of the MMC/SD module on the i.MX1 and i.MXL processors. The i.MX21 is referenced
in [6].
Table 3. i.MX1 Frequency Range
Card Type
Method
Size (Block Size)
Minimum
Maximum
MMC
Polling
Single
4 MHz
20 MHz
MMC
Polling
Multiple
4 MHz
20 MHz
MMC
DMA
Single
4 MHz
20 MHz
MMC
DMA
Multiple
4 MHz
20 MHz
SD (1-Bit Mode)
Polling
Single
4 MHz
25 MHz
SD (4-Bit Mode)
Polling
Single
8 MHz
25 MHz
SD
Polling
Multiple
–
–