Seagate STT8000A manual Mode Parameter Header, Mode Block Descriptor

ATAPI Interface Chapter 5

Mode Parameter Header

The following table describes the Mode Parameter header.

Byte	Description	Value	Meaning
0	Mode Data Length	NN	Select: Reserved
			Sense: Length of Available Following Data
1	Medium Type	NN	Tape type
2	Device Specific Parameters	WP,001,Speed	Bit 7 = Write Protect, Bits 6-4 = 001, Bits 3-
			0 = Speed Selection
3	Block Descriptor Length	00/08h	If 8, Block Descriptor follows

The only supported Buffered Mode (bits 6-4 of byte 2) is 001, indicating that write operations are buffered. Only the Speed Selection field can be changed.

The following table defines the tape speeds supported with QIC-3095 tapes.

Speed	Tape Speed	Transfer Rate
0000b	Automatic	Automatic
0001b	46 ips	489 Kbytes/sec
0010b	69 ips	733 Kbytes/sec
0011b	92 ips	1,000 Kbytes/sec

Mode Block Descriptor

The Block Descriptor is returned to the MODE SENSE command unless the DBD bit in the command packet is set to one. If the Block Descriptor is not sent, the Block Descriptor Length field (in the Mode Parameter Header) is 0.

Byte	Description	Value	Meaning
4	Density Code	NN	Current Density
5-7	Number of Blocks	000000h	Zero
8	Reserved	00h	—
9-11	Block Length	000200h Always 512 byte blocks

The Number of Blocks is 0, indicating that all blocks in the media match this descriptor, (the blocks are fixed 512 byte blocks).

None of the Block Descriptor parameters may be changed (Block Length is fixed).

STT8000A Product Manual Page 49