Sony SDX-800V/R Mode Fixed Bit in Read, Write Block Length, Mode Select Page Header Bit Byte

6.Command Specification MODE SELECT

Block length: The Block Length field specifies the length in bytes of each logical block transferred over the SCSI bus. A block length of ZERO indicates that the length is variable. Any other value indicates the number of bytes per block that the drive must handshake over the bus. This establishes block length such that the transfer length for read, write type commands will be a block count not a byte count.

Note: It is value of this field together with the Fixed Bit Field in the READ, or WRITE commands that determine whether the drive is in Fixed or Variable block mode.

Mode	Fixed Bit in Read, Write	Block Length in
		Mode Select/Sense
Fixed Block	1	Block Size
Variable Block	0	0

The default fixed block size is 0 bytes however, if a fixed command (fixed bit of ONE) is received, the drive will return the CHECK CONDITION status with an ILLEGAL REQUEST sense key and the additional sense code shall be set to COMMAND SEQUENCE ERROR.

Note: Minimum block-size is 4. The figures must be multiples of 4, otherwise CHECK CONDITION status will be return, and Sense Key will be ILLEGAL REQUEST.

Following the Block Descriptor are the MODE SELECT pages. They are the method by which the device parameters are set. Each page has a two byte header which identifies the page code and indicates the number of bytes in that page.

Table 6-38: MODE SELECT Page Header

Bit	7	6	5	4	3		2	1	0
Byte
0	PS	Reserved			Page	Code
1				Additional Page Length

PS: when the Page Savable bit is set, this indicates that the page contains saved parameters. This bit will never be set as there is no non-volatile RAM on the drive into which parameter data may be saved.

The page codes that are supported are:

Table 6-39: Supported MODE SELECT Page Codes

Page Code	Description
00h	Standard Sense
02h	Disconnect-Reconnect
0Ah	Control Mode Page
0Fh	Data Compression Control
10h	Device Configuration
11h	Medium Partitions Parameter
1Ch	Information Exception Control
31h	AIT Device Configuration
32h	Append Partition (not support)
33h	Delete Partition (not support)
3Fh	Return All Pages

Additional Page Length: Indicates the number of bytes in that page. The value does not, however, include bytes 0 and 1. The length is returned on MODE SENSE and must subsequently be set to the same value when performing

MODE SELECT.

If the page length does not match that expected by the drive a CHECK CONDITION status is returned with the sense key to set to ILLEGAL REQUEST.

The drive also returns a CHECK CONDITION status with an ILLEGAL REQUEST sense key if the Host sends an unsupported Page Code, a page field with values that are not supported or are not changeable. In this case, no parameters will have been changed by the command.

6-40 SONY AIT-3Ex drive SDX-800V series Ver.1.1