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READ BUFFER Command (3Ch) SDLT 600 SCSI Interface Guide

4-184 January 2005 81-81200-02 REV A01

Table 4-107. READ BUFFER Command Descriptor Block — Field Descriptions

Field Name Description

Mode The drive supports the following values for this field. Setting any non-

supported value causes the drive to terminate the command with a CHECK

CONDITION status and Sense Key set to ILLEGAL REQUEST.

Mode Description

00h Combined Header and Data Mode (see page 4-186)

02h Data Mode (see page 4-187)

03h Descriptor Mode (see page 4-187)

0Ah Read Data from Echo Buffer (see page 4-187)

0Bh Echo Buffer Descriptor Mode (see page 4-188)

Buffer ID Indicates from which buffer the data is to be transferred. Possible values are:

Buffer Description

00h This 2,200 KB buffer is used with the WRITE BUFFER

command to provide a diagnostic capability for testing the SCSI

bus, hardware integrity, or both.

01h This buffer is used to read the drive’s SCSI RAM and EEPROM.

Its effective size is 30200h bytes.

02h This buffer is used to read the drive’s data cache RAM. The

Available Length field returned in Combined Header and Data

mode and the Buffer Capacity field returned in Descriptor mode

are not large enough to express the size of the data cache RAM, so

both fields return to 0.

03h This buffer is used to read the DMARK table.

A1h This buffer provides access to diagnostic information saved from

an earlier event. (Saved Buffer.)

A2h This buffer provides real-time access to diagnostic information.

(Live Buffer.)

Note: In Data mode or Combined Header and Data mode, any other value

besides those listed is illegal. In Descriptor mode, any other value

returns all zeros in the descriptor. In Read Data from Echo Buffer and

Echo Buffer Descriptor modes, this field is ignored.

Buffer Offset Allows the host to specify the location of the start of the data within the buffer.

This field is reserved and must be set to 0 for all modes except Data and

Descriptor modes.

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Quantum 1200 Series DAT Autochanger Betriebsanweisung Seite 226