Product manual
3.12 Detailed SD Card Structure
!S THE TOPIC OF THIS BOOK IS 3$ CARDS THE INTERNAL STRUCTURE AND THE USE OF THESE CARDS IN 0)#
MICROCONTROLLERBASED SYSTEMS WILL BE DESCRIBED IN THIS SECTION
3.12.1 SD Card Pin Configuration
&IGURE SHOWS THE PIN CONlGURATION OF A STANDARD 3$ CARD 4HE CARD HAS NINE PINS AS
SHOWN IN THE lGURE AND A WRITEPROTECT SWITCH TO ENABLEDISABLE WRITING ONTO THE CARD
! STANDARD 3$ CARD CAN BE OPERATED IN TWO MODES THE SD Bus mode AND THE SPI Bus mode
3$ "US MODE IS THE NATIVE OPERATING MODE OF THE CARD AND ALL THE PINS ARE USED IN THIS MODE
$ATA IS TRANSFERRED USING FOUR PINS $n$ A CLOCK #,+ PIN AND A COMMAND LINE #-$
$ATA CAN BE TRANSFERRED FROM THE CARD TO THE HOST OR VICE VERSA OVER THE FOUR DATA LINES
&IGURE SHOWS THE 3$ CARD CONNECTION IN 3$ "US MODE
30) "US MODE IS THE MORE COMMONLY USED MODE AND IT ALLOWS DATA TO BE TRANSFERRED
ON TWO LINES $/ AND $) IN SERIAL FORMAT USING A CHIP SELECT #3 AND A #,+ LINE 4HE
30) MODE IS EASIER TO USE BUT IT HAS THE DISADVANTAGE OF REDUCED PERFORMANCE COMPARED
WITH THE 3$ MODE OF OPERATION &IGURE SHOWS THE 3$ CARD CONNECTIONS IN 30) MODE
3$ CARD PINS HAVE DIFFERENT MEANINGS DEPENDING UPON THE MODE OF OPERATION 4ABLE SHOWS
THE PIN ASSIGNMENTS WHEN THE CARD IS OPERATED IN 3$ "US AND 30) "US MODES
4HE PROJECTS IN THIS BOOK ARE BASED ON THE OPERATIONS IN THE 30) "US MODE 4HE FOLLOWING PINS
ARE USED IN 30) "US MODE
#HIP SELECT n 0IN s
$ATA IN n 0IN s
#LOCK n 0IN s
$ATA OUT n 0IN s
Figure 3.11: Standard SD Card Pin Configuration
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