5.4 Command Protocol
f)The drive clears DRQ bit to 0. If transfer of another sector is requested, the device sets the BSY bit and steps d) and after are repeated.
Even if an error is encountered, the device prepares for data transfer by setting the DRQ bit. Whether or not to transfer the data is determined for each host. In other words, the host should receive the relevant sector of data (512 bytes of uninsured dummy data) or release the DRQ status by resetting.