SD Card Pinout
Full-size Secure Digital memory card with a 9-contact SD/SPI interface.
Overview
The standard (full-size) SD card exposes nine edge contacts and supports two protocols on the same contacts: native SD/SDIO (1-bit or 4-bit data bus with a command line) and the simpler legacy SPI mode.
Pin functions differ by mode. In SD mode pin 1 doubles as card-detect and data 3; in SPI mode it becomes chip-select. SPI mode uses only DAT0 (DO) and the command line as DI.
Pinout
| Pin | Name | Function | Description |
|---|---|---|---|
| 1 | CD/DAT3 (SD) / CS (SPI) | SPI / DATA | Card detect & data 3 / SPI chip select |
| 2 | CMD (SD) / DI (SPI) | SPI / DATA | Command-response line / SPI data in (MOSI) |
| 3 | VSS1 | GND | Ground |
| 4 | VDD | POWER | Supply voltage (2.7-3.6 V) |
| 5 | CLK (SD) / SCLK (SPI) | SPI / CLK | Clock |
| 6 | VSS2 | GND | Ground |
| 7 | DAT0 (SD) / DO (SPI) | SPI / DATA | Data 0 / SPI data out (MISO) |
| 8 | DAT1 (SD) / RSV (SPI) | SPI / DATA | Data 1 / reserved (IRQ in SDIO) |
| 9 | DAT2 (SD) / RSV (SPI) | SPI / DATA | Data 2 / reserved |
Notes
- 1-bit SD and SPI modes use only DAT0; 4-bit SD mode uses DAT0-DAT3.
- UHS-II cards add a second row of contacts not listed here.
Reference: SD Association - SD Physical Layer Simplified Specification· verified 2026-06-27