Speed Modes

Versal ACAP Technical Reference Manual (AM011)

Document ID
AM011
Release Date
2022-04-26
Revision
1.4 English
The SD card speed modes are listed in the following table.
Table 1. SD Card Speed Modes
Speed Mode 1 Data Rate Clock Edge I/O Width Frequency (MHz) Clock Source Max. MB/s SD Card Voltage MIO/EMIO
Default speed 2 Single Falling 1, 4 25 DIV_CLK 12.5 3 3.3V MIO, EMIO
High speed Single Rising 1, 4 50 DLL Clock 25 4 3.3V MIO
SDR-12 Single Rising 4 25 DIV_CLK 12.5 1.8V MIO, EMIO
SDR-25 Single Rising 4 50 DLL Clock 25 1.8V MIO
DDR-50 Double Both 4 50 DLL Clock 50 1.8V MIO
SDR-50 Single Rising 4 100 DLL Clock 50 1.8V MIO
SDR-104 Single Rising 4 200 DLL Clock 100 1.8V MIO
  1. SD line selection is based on SD 2.0 or 3.0 mode.
  2. When using an external voltage level shifter, the maximum frequency is 20 MHz.
  3. Throughput is reduced to 3.125 MB/s in 1-bit mode.
  4. Throughput is reduced to 6.25 MB/s in 1-bit mode.
The MMC and eMMC speed modes are listed in the following table.
Table 2. MMC and eMMC Speed Modes
Speed Mode Data Rate Clock Edge I/O Width Frequency (MHz) Clock Source Max. MB/s 3 SD Card Interface Voltage MIO/EMIO
Legacy MMC speed 1 , 2 Single Falling 1, 4, 8 25 DIV_CLK 25 1.8, 3.3V MIO, EMIO
HS-SDR Single Rising 4, 8 50 DLL Clock 50 1.8, 3.3V MIO
HS-DDR Double Both 4, 8 50 DLL Clock 100 1.8, 3.3V MIO
HS-200 Single Rising 4, 8 200 DLL Clock 200 1.8V MIO
  1. Legacy MMC speed relates to default MMC speed.
  2. The default eMMC boots in legacy MMC speed mode only. Software driver can switch to the high-speed modes for higher throughput.
  3. Throughput is based on an 8-bit I/O interface width.