8.2.5. WRITE AND VERIFY Command

     Peripheral Device Type:  Direct Access
        Operation Code Type:  Optional

                     Table 8-38: WRITE AND VERIFY Command

==============================================================================
  Bit|   7    |   6    |   5    |   4    |   3    |   2    |   1    |   0    | 
Byte |        |        |        |        |        |        |        |        |
==============================================================================
 0   |                           Operation Code (2Eh)                        | 
-----|-----------------------------------------------------------------------|
 1   |   Logical Unit Number    |   DPO  |   FUA  | WrtSme | BytChk | RelAdr |
-----|-----------------------------------------------------------------------|
 2   | (MSB)                                                                 |
-----|---                                                                 ---|
 3   |                                                                       |
-----|---                        Logical Block Address                    ---|
 4   |                                                                       |
-----|---                                                                 ---|
 5   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 6   |                           Reserved                                    |
-----|-----------------------------------------------------------------------|
 7   | (MSB)                                                                 |
-----|---                        Transfer Length                             |
 8   |                                                                 (LSB) |
-----|-----------------------------------------------------------------------|
 9   | Vendor Unique   |         Reserved                  |  Flag  |  Link  |
==============================================================================

  The WRITE AND VERIFY command (Table 8-28) requests that the target write the 
data transferred from the initiator to the medium and then verify that the 
data is correctly written.

  A byte check (BytChk) bit of zero causes the verification to be simply a 
medium  verification  (CRC, ECC, etc) a medium verification  to  be  performed 
according  to  the  criteria specified in the MODE  SELECT  command.  No  data 
transfer  is performed.  A BytChk bit of one causes a byte-by-byte compare  of 
data  written  on  the peripheral device and the  data  transferred  from  the 
initiator.   If the compare is unsuccessful, the command shall  be  terminated 
with a CHECK CONDITION status and the sense key shall be set to MISCOMPARE.

  The logical block address specifies the logical block at which the write 
operation shall begin.

  The transfer length specifies the number of contiguous logical blocks of 
data that shall be transferred.  A transfer length of zero indicates that no 
logical blocks shall be transferred.  This condition shall not be considered 
as an error and no data shall be written.  Any other value indicates the 
number of logical blocks that shall be transferred.

See section 6.2.4 for a description of the cache control bits (DPO and FUA).  
See section 6.2.5 for a description of the relative address bit (RelAdr).

  A Write Same (WRTSME) bit of zero causes the command to be done as a normal 
WRITE.  A WRTSME bit of one causes a Write Same capability to occur.  Only one 
logical block of data shall be sent during the Data Out Phase, regardless of 
the transfer length.  The transfer length specifies the number of contiguous 
logical blocks to be written. All logical blocks written shall be written with 
the same data as the first logical block.  A transfer length of zero shall be 
handled different when the WRTSME bit is one.  A transfer length of zero shall 
represent that the data be continuously written from the logical block address 
specified in the command block until the last logical block addressable.

  IMPLEMENTOR'S  NOTE:  The WRITE AND VERIFY command does not imply  that  the 
  data shall be transfered twice (i.e., once for the write pass, and once  for 
  the  verify  pass)  when  performing a byte  compare.  If  the  user  wishes 
  guarantee  that  two transfers occur (e.g., to ensure the integrity  of  the 
  path to the media), then the user should issue a WRITE command with the LINK 
  bit  set  followed by a VERIFY command, transfering the same  data  on  each 
  command.