Appendix B – ATWILC SDIO Communication

SDIO protocol provides communication over the SD bus and is based on command and data bit streams that are initiated by a Start bit and terminated by a Stop bit.

Command is a token that starts an operation. A command is sent from the host either to a single card (addressed command) or to all connected cards (broadcast command). A command is transferred serially on the CMD line.

Response is a token that is sent from an addressed card, or (synchronously) from all connected cards, to the hosts as an answer to a previously received command. A response is transferred serially on the CMD line.

Data can be transferred from the card to the host or vice versa. Data is transferred via the data lines.

Data transfer to/from the SD Card are done in blocks. Data blocks are always succeeded by CRC bits. Single and multiple block operations are defined.