Parameter List Length (Page Format)

The Parameter List Length byte indicates the length of the parameter list that will be transferred from the initiator to the EXB-8500 during the Data Out phase. When the PF bit is set to 1 (page format), all parameters after the Block Descriptor are transferred as pages of related parameters. The value of the Parameter List Length byte depends on which combination of parameter pages is being transferred. The value for this byte must represent the total number of bytes to be transferred from the initiator to the EXB-8500. Table 12-2 shows the number of bytes that should be designated to transfer the various types of MODE SELECT parameter segments. When the value for the Parameter List Length byte is 0, no data is transferred from the initiator. A value of 0 for this byte is not an error.

To transfer these

parameters... Designate this amount

No parameter list data 0 bytes (0h)

Parameter List Header 4 bytes (4h)

Block Descriptor 8 bytes (8h)

Read-Write Error Recovery Page (Page Code=01h) + 9 bytes (09h) Disconnect-Reconnect Page (Page Code=02h) + 12 bytes (0Ch) Data Compression Page (Page Code=0Fh) + 16 bytes (10h) Device Configuration Page (Page Code=10h) + 15 bytes (0Fh) Vendor Unique Parameters Page 1 (Page Code=20h) + 6 bytes (06h) Vendor Unique Parameters Page 2 (Page Code=21h) + 6 bytes (06h)

Examples To transfer the Parameter List Header, the Block Descriptor, and the Vendor Unique Parameters Page 1:

1. Specify 12h for the Parameter List Length byte (04h for the

Parameter List Header + 08h for the Block Descriptor + 06h for the Vendor Unique Parameters Page 1).

2. Set the Block Descriptor Length byte in the Parameter List Header to 08h.

To transfer the Parameter List Header and the Read-Write Error Recovery page:

1. Specify 0Dh for the Parameter List Length byte (04h + 09h). 2. Set the Block Descriptor Length byte in the Parameter List Header

to 00h.

Table 12-3 summarizes the values you should designate for the Parameter List Length byte when you want to transfer the Parameter List Header, the Block Descriptor, and only one of the parameter pages. You can use this table as a quick reference when you are interested in changing the parameters for only one of the MODE SELECT pages.

Designate this amount...

For this page plus the Parameter List Header and Block Descriptor

15h Read-Write Error Recovery Page (Page Code=01h) 18h Disconnect-Reconnect Page (Page Code=02h) 1Ch Data Compression Page (Page Code=0Fh) 1Bh Device Configuration Page (Page Code=10h)

12h Vendor Unique Parameters Page 1 (Page Code=20h) 12h Vendor Unique Parameters Page 2 (Page Code=21h) Table 12-3 Values to Designate for Parameter List Length (Page Format)

Restrictions for MODE SELECT Data in Page Format The following restrictions apply to transfers of parameter list data when the PF bit is 1:

For any data transfer greater than 0 bytes, the entire 4-byte Parameter List Header must be transferred. That is, the entire 4-byte Parameter List Header must be transferred before the Block Descriptor or any parameter page can be transferred.

The Block Descriptor and any parameter pages must be transferred in their entirety; partial transfers of these data segments are not allowed.

Note: Any value for the Parameter List Length that causes the Parameter List Header, Block Descriptor, or one of the parameter pages to be truncated will terminate the command with Check Condition status. The sense key will be set to Illegal Request and the Additional Sense Code will be set to Parameter List Length Error.

Various combinations of the Parameter List Header, Block Descriptor, and parameter pages can be transferred based on these restrictions.

Byte 05, Bits 7 and 6 - Vendor Unique

12.2 Parameter List Header

(Non-Page and Page Formats)

02 RSVD Buffered Mode Speed

03 Block Descriptor Length

Field Definitions

The Parameter List Header is the same for both non-page and page formats.

Byte 02, Bits 6 through 4 - Buffered Mode

The EXB-8500 supports two data transfer modes, as follows: 000 – Unbuffered mode

001 – Buffered mode

In buffered mode, data from a WRITE command and filemarks from a WRITE FILEMARKS command (EXB-8500 format only) are held in the EXB-8500’s buffer until one of the following events causes the data and filemarks to be written to the tape:

The motion threshold is reached.

The EXB-8500 receives one of the following commands:

❏ REWIND (01h)

❏ WRITE FILEMARKS (10h) non-immediate

❏ SPACE (11h) in either direction

❏ ERASE (19h)

❏ LOAD/UNLOAD (1Bh)

❏ LOCATE (2Bh) in the reverse direction. The operator presses the unload button.

The time specified for the Write Delay Time field elapses (note, however, if the Write Delay Time field is 0, a partially full buffer is not flushed to tape).

Note: The Write Delay Time field can be set for page format only; see Section 12.8 for more information.

In buffered mode, status is returned when the last block of data has been transferred to the EXB-8500’s buffer. In unbuffered mode, status is returned only after the data has actually been written to the tape.

The power-on default value for the Buffered Mode field is 001.

Byte 02, Bits 3 through 0 - Speed

The EXB-8500 does not support any operations at different speeds. All operations have a defined speed that cannot be modified by this command. The valid value for this field is 0.