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DISK DRIVE OPERATION 
 

SpinPoint V40 Product Manual 

66

 

6.4.16  Read Verify Sector(s) (40h:with retry,  41h:without retry) 

 
This command is identical to the Read Sectors command, except that DRQ is never set, and no data is 
transferred to the host. See 6.6.3 for the protocol. When the command is accepted, the drive sets BSY. 
 
When the requested sectors have been verified, the drive clears BSY and generates an interrupt. Upon 
command completion, the Command Block registers contain the cylinder, head, and sector number of the last 
sector verified in CHS mode or of the logical block address in LBA mode. If an error occurs, the Verify 
terminates at the sector where the error occurred.  
 
The Command Block registers contain the cylinder, head, and sector number in CHS mode, or the logical 
block address in LBA mode where the error occurred. The Sector Count register contains the number of 
sectors not yet verified. 
 

 
This command moves the read/write heads from anywhere on the disk to cylinder 0. Upon receipt of the 
command, the drive sets BSY and issues a seek to cylinder zero. The drive then waits for the seek to 
complete before updating status, clearing BSY, and generating an interrupt. If the drive cannot reach cylinder 
0, it posts a Track 0 Not Found error. 
 

 
This command initiates a seek to the track and selects the head specified in the command block. The drive 
need not be formatted for a seek to execute properly. Refer to section 6.6.3 for the protocol. The drive shall 
not set DSC=1 until the action of seeking has completed. The drive may return the interrupt before the seek is 
completed. 
 
If another command is issued to the drive while a seek is being executed, the drive sets BSY=1, waits for the 
seek to complete, and then begins execution of the command.