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DISK DRIVE OPERATION 

 

SpinPoint V40 Product Manual

65

 

 
This command returns the native maximum address.  The native maximum address is the highest address 
accepted by the device in the factory default condition.  The native maximum address is the maximum 
address that is valid when using the SET MAX ADDRESS command. 
 
Normal Output: 
 
Sector Number -  

maximum native sector number (IDENTIFY DEVICE word 6) or LBA bits (7:0) for native max 
address on the device. 

Cylinder Low -  

maximum native cylinder number low or LBA bits (15:8) for native max address on the device. 

Cylinder High -  

maximum native cylinder number high or LBA bits (23:16) for native max address on device. 

Device/Head -  

maximum native head number (IDENTIFY DEVICE word 3 minus one) or LBA bits (27:24) for 

native max address on the device. 

DEV shall indicate the selected device. 

Status register - 

BSY shall be cleared to zero indicating command completion. 
DRDY shall be set to one. 
DF (Device Fault) shall be cleared to zero. 
DRQ shall be cleared to zero. 
ERR shall be cleared to zero. 

 
 

6.4.15  Read Sector(s) (20h:with retry,  21h:without retry) 

 
This command reads from 1 to 256 sectors as specified in the Sector Count register. A sector count of 0 
requests 256 sectors. The transfer begins at the sector specified in the Sector Number register. See 6.6.1 for 
the DRQ, IRQ and BSY protocol on data transfers. 
 
If the drive is not already on the desired track, an implied seek is performed. Once at the desired track, the 
drive searches for the appropriate ID field. 
 
If retries are disabled and two index pulses have occurred without error free reading of the requested ID, an 
ID Not Found error is posted.  If retries are enabled, a vender-specified number of attempts are made to read 
the requested ID before posting an error. 
 
If the ID is read correctly, the data address mark shall be recognized within a specified number of bytes, or 
the Address Mark Not Found error is posted. DRQ is always set prior to data transfer, regardless of the 
presence or absence of an error condition. 
 
At command completion, the Command Block registers contain the cylinder, head, and sector number of the 
last sector read in CHS mode or of the logical block address in LBA mode. 
 
If an error occurs, the read terminates at the sector where the error occurred. The Command Block registers 
contain the cylinder, head, and sector number of the sector where the error occurred in CHS mode or of the 
logical block address in LBA mode. The flawed data is pending in the sector buffer.