Secure Digital Card
Secure Digital [SD] is a flash based removable memory card. The card
format may also be used other device functions in addition to data
storage. Secure Digital uses a 9-Pin connector [1 rows of 9 pins]. A
compatible card format is called Secure Digital I/O [SDIO]. Refer to the SDIO page for information on that
card standard.
The Secure Digital card dimensions are: 24mm wide x 32mm long.
The Secure Digital I/O card dimensions are: 24mm wide x 32mm long x 2.1mm
thick.
There are two types of SDIO cards; a full-speed version, and a slow-speed
version. The full-speed version will operate with a 1-bit and 4-bit SD
transfer mode, both with a clock ranging from 0Hz to 25MHz. The 4-bit
version operating at 25MHz has a transfer rate of 100Mbps. The slow-speed
version will use the 1-bit mode and may have the 4-bit mode, but only
operates at a transfer rate of between 0Hz and 400kHz. The slow-speed
version is not intended for memory functions. The SDIO card support the
SPI bus interface. The SDIO mechanical form factor is shown above;
however a few gaps "lock notches" are not shown. The SDIO card may exceed
24mm in width after 37mm in length, and the width may be thicker then
2.1mm after 37mm in length
| Pin # | Pin Name | SD Signal Function SD Mode | SPI Signal Function SPI Mode |
| 1 | DAT3/CS | Data Line 3 | Chip Select/Slave Select [SS] |
| 2 | CMD/DI | Command Line | Master Out/Slave In [MOSI] |
| 3 | VSS1 | Ground | Ground |
| 4 | Vdd | Voltage Supply [2.7v or 3.6v] | Voltage Supply [2.7v or 3.6v] |
| 5 | Clock | Clock | Clock [SCK] |
| 6 | Vss2 | Ground | Ground |
| 7 | DAT0/D0 | Data Line 0 | Master In Slave Out [MISO] |
| 8 | DAT1/IRQ | Data Line 1 | Unused or IRQ |
| 9 | DAT2/NC | Data Line 2 | Unused |
| Pin # |
SD 4-bit Mode |
SD 1-bit Mode |
SPI Mode |
|||
| 1 | CD/DAT[3] | Data Line 3 | N/C | Not Used | CS | Card Select |
| 2 | CMD | Command Line | CMD | Command Line | DI | Data Input |
| 3 | VSS1 | Ground | VSS1 | Ground | VSS1 | Ground |
| 4 | VDD | Supply Voltage | VDD | Supply Voltage | VDD | Supply Voltage |
| 5 | CLK | Clock | CLK | Clock | SCLK | Clock |
| 6 | Vss2 | Ground | Vss2 | Ground | Vss2 | Ground |
| 7 | DAT[0] | Data Line 0 | DATA | Data Line | DO | Data Output |
| 8 | DAT[1] | Data Line 1 / Interrupt | IRQ | Interrupt | IRQ | Interrupt |
| 9 | DAT[2] | Data Line 2 /Read Wait | RW | Read Wait | NC | Not Used |
The graphic below provides a comparison of the different Removable memory
Card standards. Many of the different Memory Card standards have
descriptions listed on this web site. The different standards based on
card size are provided. Refer to the Personal Computer Buses page
for more information for different memory types, as listed here.
Refer to this page for a list of different Flash Memory Stick Formats.