The PmodSD connects to all communication and power signals from a standard SD card and brings them out to the 2x6 pin header on the board. The pinout placement on the PmodSD is designed to readily communicate with a Digilent system board via SPI. The SPI interface standard uses four signal lines: SS (slave select), MOSI (master out slave in), MISO (master in slave out), and SCK (serial clock). SD cards can also be driven in a native mode that also uses the DAT1 and DAT2 signals as well as the DAT0, DAT3, CMD, and CLK signals. The WP signal can be set by a switch on the SD card to prevent the host from writing or erasing data on the card. The CD signal can be used by the host to indicate that a card is in the SD slot and is detectable.
嵌入式设计与开发