11. Protocol

Commands can be grouped into different classes according to the protocols used for command execution. The command classes with their associated protocols are defined below.

For all commands, the host first checks BSY bit and DRDY bit. If BSY＝1, the host should proceed no further unless and until the BSY＝0, and the DRDY＝1.

Interrupts are cleared when host reads Status register, issues a reset, or writes to the Command register. Interrupts are not cleared when host reads Alternate Status register.

A command shall only be interrupted with a hardware or software reset. The result of writing to the command register while BSY＝1 or DRQ＝1 is unpredictable and may result in data corruption. Therefore, a command should only be interrupted by a reset at times when the host judges that there is a problem, such as receiving no response from a drive. Host programmers should set command time-out periods enough long in order to avoid having effect on the device's ability to perform level retry and data recovery activities.

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