User Manual

SCSI Commands Reference Manual, Rev. J 199

www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)

3.40 REZERO UNIT command

This command has been declared obsolete by the T10 committee. However, it is included because it may be implemented on

some products.

The Rezero Unit command (see table 168) requests that the disk drive set its logical block address to zero and return the disk

drive read/write heads to the track (or cylinder) containing Logical Block Zero. This command is intended for systems which

disable retries and the initiator performs error recovery. It is longer than a seek to Logical Block Address zero and should be

utilized if seek errors are encountered.

For systems that support disconnection, the disk drive disconnects when this command is received.

A Rezero Command also causes a thermal compensation to occur and resets the thermal compensation cycle timer back to its

start, thus allowing the host to know when to expect the next thermal compensation to occur. The host can thus prevent critical

data transfer operations from being interrupted at an undesirable time.

For drives that support saved log parameters, the Rezero Unit command will also save log counters to the media and reset the

log save timer back to its start.

LUN (Logical Unit Number) field

Seagate drives only support Logical Unit Number 0.

CONTROL byte

The CONTROL byte is described in clause 2.2.7.

Table 168 REZERO UNIT command (01h)

Bit

Byte

7 6 5 4 3 2 1 0

OPERATION CODE (01h)

LUN

LOGICAL BLOCK ADDRESS MUST BE 0’S

Reserved

CONTROL