MultiMediaCard Protocol - USB Mass Storage: Designing and Programming Devices and Embedded Hosts - page 105

the received data into the storage media. There is no specified maximum
time to wait for DataOut to return high.
After a command completes, the host generates at least 8 clock cycles before
sending a new command. There is no maximum number of clock cycles
before the next command. The host can bring CS high on the last clock
transition of the last byte that is part of the command's communications
(before the final 8 clock cycles) or any time after this (NEC and NDS). In a
block-write operation, the host can bring CS high while the card is busy
programming, and bring CS low again later to verify that DataOut is high,
indicating that the write operation completed.
Commands with No Data Transfer
On an SPI bus, a command with no data transfer has these steps:
1. The host brings CS low.
2. The host sends the 48-bit command and continues to generate clock
cycles.
3. After receiving the command followed by 8 to 64 clock cycles, the card
sends the command's response.
4. The host can bring CS high any time after receiving the response.
5. The host generates 8 clock cycles to complete the command.
Commands that Read Data from the Storage Media
On an SPI bus, a command that requests a single data block from the stor-
age media has these steps:
1. The host brings CS low.
2. The host sends the 48-bit command and continues to generate clock
cycles.
3. After receiving the command followed by 8 to 64 clock cycles, the card
sends the command's response.
4. The host continues to generate clock cycles.
5. After between 8 clock cycles and the card-specific access time, the card
sends the requested data block. On error, the card sends a data_error token
instead of a data token.