SPRUJ17H March 2022 – October 2024 AM2631 , AM2631-Q1 , AM2632 , AM2632-Q1 , AM2634 , AM2634-Q1
The bus protocol between the MMC/SD/SDIO host controller and the card is message-based. Each message is represented by one of the following parts:
Command: A command starts an operation. The command is transferred serially from the MMC/SD/SDIO host controller to the card on the mmc_cmd line.
Response: A response is an answer to a command. The response is sent from the card to the MMC/SD/SDIO host controller. It is transferred serially on the mmc_cmd line.
Data: Data are transferred from the MMC/SD/SDIO host controller to the card or from a card to the MMC/SD/SDIO host controller using the DATA lines.
Busy: The mmc_dat0 signal is maintained low by the card as far as it is programming the data received.
CRC status: CRC result is sent by the card through the mmc_dat0 line when executing a write transfer. When a transmission error occurs on any of the active data lines, the card sends a negative CRC status on mmc_dat0. When a successful transmission occurs over all active data lines, the card sends a positive CRC status on mmc_dat0 and starts the data programming procedure.