Specifications

ATAPI For Streaming Tape QIC-157 Rev B

6.8.9. READ Command

The READ command requests that the Device transfer one or more block(s) of data to the Host

beginning with the current block.

Table 6-57 Read Command

Bit

Byte

7 6 5 4 3 2 1 0

0 Operation code (08h)

1 Reserved Reserved

(SILI)

1 (Fixed)

2 (MSB)

3 Transfer Length

4 (LSB)

5 Reserved

6 Reserved

7 Reserved

8 Reserved

9 Reserved

10 Reserved

11 Reserved

The Transfer Length specifies the number of fixed-length blocks to be transferred, using the current

block length reported in the mode parameters block descriptor.

A successful READ command shall transfer the requested Transfer Length times the current block

length in bytes. Upon completion, the logical position shall be after the last block transferred (end-of-

partition side).

If an incorrect length block is read, “Check Condition” status shall be returned and the ILI and Valid

bits shall be set to one in the sense data. Upon termination, the logical position shall be after the

incorrect length block (end-of-partition side). The Information field shall be set to the difference

(residue) of the requested Transfer Length minus the actual number of blocks read (not including the

incorrect length block).

A Transfer Length of zero indicates that no data shall be transferred. This condition shall not be

considered an error and the logical position shall not be changed but the Device shall start a read

ahead mode of operation. The DSC bit is set when sufficient data is available in the ATAPI device’s

data buffer.

If the Device encounters a filemark during a READ command, “Check Condition” status shall be

returned and the filemark and Valid bits shall be set to one in the sense data. The Sense Key shall be

set to NO SENSE or RECOVERED ERROR, as appropriate. Upon termination, the logical position

shall be after the filemark (end-of-partition side). The Information field shall be set to the difference

(residue) of the requested Transfer Length minus the actual number of blocks read (not including the

filemark).

Upon termination, the logical position shall be after the last block transferred or the block with an

unrecovered read error (end-of-partition side). The Information field shall be set to the difference

(residue) of the requested Transfer Length minus the actual number of blocks read.

If the Device encounters end-of-data during a READ command, “Check Condition” status shall be

returned, the Sense Key shall be set to BLANK CHECK, and the Valid bit shall be set to one in the