Exabyte EXB-8205 Instruções de Operação descarregar pdf (Página 231)

Byte 01, Bit 0 - Fixed

The Fixed bit defines the type of read operation being performed, as

follows:

0 – A single logical block is read, and the length of this block is

specified in the Transfer Length field.

1 – One or more fixed-length logical blocks are read, and the number

of blocks is specified in the Transfer Length field. The length of

each block is either the power-on default block length or the

length specified with the currently active MODE SELECT

parameters (bytes 5 through 7 of the Block Descriptor).

Note: The CTS returns Check Condition status with the sense key

set to Illegal Request (5h) if the Fixed field in the READ

command is 1 (fixed-length logical blocks) and the Block

Length field in the current MODE SELECT data is 0

(variable-length logical block).

The ASC and ASCQ bits are set to 81h and 00h (fixed/variable

mismatch).

Bytes 02 through 04 - Transfer Length

The Transfer Length field defines the amount of data to be read, as

follows:

When the Fixed bit is set to 0, the Transfer Length field contains

the length of the logical block in bytes. The logical block can be

any size from 0 to 240 Kbytes.

When the Fixed bit is set to 1, the Transfer Length field contains

the number of logical blocks to be read. The block length is the

length specified with the MODE SELECT command. The

allowable block sizes are defined by the READ BLOCK LIMITS

(05h) command.

The data is read from the next logical block on the tape and is

transferred to the initiator.

Note: When the value for the Transfer Length field is 0, no data is

transferred and the current position of the tape is not changed.

A value of 0 for these bytes is not an error.

Byte 05, Bits 7 and 6 - Vendor Unique

There are no vendor unique definitions for this command.

May 1994 EXB-8205 and EXB-8505

(Standard and XL)

12-3

12 READ (08h)

1 2 ... 226 227 228 229 230 231 232 233 234 235 236 ... 445 446

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Exabyte EXB-8205 Instruções de Operação Página 231