Fujitsu M2488 manual Block ID Format Field Description, Format Mode Values, Format Code Value

TAPE UNIT SCSI COMMANDS M2488 PRODUCT GUIDE

Table 4-27. Block ID Format Field Description

BYTE	BIT	VALUE	DESCRIPTION
0	0-6		The Physical reference field can either be 0 or in the range 1 to 95.
		0	The value 0 indicates that a valid physical reference value is not known for the
			target position.
		1 to 95	The values in the range 1 to 95 indicate an approximate physical location on tape
			close to the target position. When the Physical reference value is not 0, the tape
			unit can use the value to perform a high speed locate to get close to the target
			position.
0	7		The Wrap field indicates whether the target position is in the first wrap or second
			wrap a of tape.
		0	If Wrap equals 0 then the target position is in the first wrap.
		1	If Wrap equals 1 then the target position is in the second wrap.
			If the wrap of the target position is unknown then the Wrap field should be set to
			0.
1	6-7		The Format code field indicates the format of the tape cartridge. The meaning of
			the possible values are described in Table 4-28.
1	0-5		A unique Logical block position is associated with each data block and filemark
2-3	0-7		written on a tape. The first filemark or data block on tape is assigned Logical
			block position 0; the Logical block position increases by 1 for each data block
			and filemark thereafter. The maximum Logical block position is 3FFFEFh.

a.A 36 track tape consists of two interleaved groups of 18 tracks; each group is called a wrap. The first wrap is written first and runs from Physical BOT towards Physical EOT. The second wrap is written second and runs from Physical EOT towards Physical BOT. The tape unit hides the transition from the first wrap to the second wrap so that the user sees an [abstract] continuous length of tape running from Logical BOT (the beginning of the first wrap) to Logical EOT (the end of the second wrap).

Table 4-28. Format Mode Values

FORMAT CODE VALUE	FORMAT
00b	18 track, non-packeted
01b	36 track, packeted
10b	18 track, packeted
11b	reserved

If the Format code field is set to 11b then the LOCATE command is rejected. The Format code field is not checked against the actual format of the tape. This field is ignored except when it con- tains the reserved value 11b.

Values for the Wrap, Physical reference and Format mode fields are reported by the READ POSI- TION command (with its BT bit set to 1.) These values are also reported in Sense data when the Sense data contains a Block ID.

4-30 CG00000-011503 REV. A April 1997