Power Pins

• VIN - this is the power pin. Since the chip uses 3-5VDC you should pick whatever the logic voltage you're using. For most Arduino's that's 5V.
• 3V3 - this is the 3.3V output from the voltage regulator, you can grab up to 100mA from this if you like
• GND - common ground for power and logic

SPI Logic Pins

All pins are 3-5V compliant and use whatever logic level is on VIN

• SCK - This is the SPI clock pin, it's an input to the chip
• MISO - this is the Microcontroller In Serial Out pin, for data sent from the SD card to your processor
• MOSI - this is the Microcontroller Out Serial In pin, for data sent from your processor to the SD card
• CS - this is the chip select pin, drop it low to start an SPI transaction. It's an input to the chip