Speed class definition

The speed class definition is for indication of the minimum performance of a card. The classes are defined based on respectively the 150kB/s base value for single data rate operation (normal mode) and 300kB/s base value for dual data rate operation. The minimum performance of the card can then be marked by defined multiples of the base value e.g. 2.4MB/s (SDR) or 4.8MB/s (DDR). Only following speed classes are defined (note that MMCplus and MMCmobile cards are always including 8bit data bus and the categories below states the configuration with which the card is operated):

Low bus category classes (26MHz clock with 4bit data bus operation)
• 2.4 MB/s (sdr) or 4.8MB/s (ddr) Class A
• 3.0 MB/s (sdr) or 6.0MB/s (ddr) Class B
• 4.5 MB/s (sdr) or 9.0MB/s (ddr) Class C
• 6.0 MB/s (sdr) or 12.0MB/s (ddr) Class D
• 9.0 MB/s (sdr) or 18.0MB/s (ddr) Class E

Mid bus category classes (26MHz clock with 8bit data bus or 52MHz clock with 4bit data bus operation):
• 12.0 MB/s (sdr) or 24.0MB/s (ddr) Class F
• 15.0 MB/s (sdr) or 30.0MB/s (ddr) Class G
• 18.0 MB/s (sdr) or 36.0MB/s (ddr) Class H
• 21.0MB/s (sdr) or 42.0MB/s (ddr) Class J

High bus category classes (52MHz clock with 8bit data bus operation):
• 24.0MB/s (sdr) or 48.0MB/s (ddr) Class K
• 30.0MB/s (sdr) or 60.0MB/s (ddr) Class M
• 36.0MB/s (sdr) or 72.0MB/s (ddr) Class O
• 42.0MB/s (sdr) or 84.0MB/s (ddr) Class R
• 48.0MB/s (sdr) or 96.0MB/s (ddr) Class T