Specifications

ATAPI For Streaming Tape QIC-157 Rev B

6.8.8. MODE SENSE Command

The MODE SENSE command provides a means for a Device to report parameters. It is a

complementary command to the MODE SELECT command.

Table 6-31 Mode Sense Command

Bit

Byte

7 6 5 4 3 2 1 0

0 Operation code (1Ah)

1 Reserved DBD Reserved

2 PC Page Code

3 (MSB) Allocation Length

4 (LSB)

5 Reserved

6 Reserved

7 Reserved

8 Reserved

9 Reserved

10 Reserved

11 Reserved

A Disable Block Descriptors (DBD) bit of zero indicates that the Device may return zero or more

block descriptors in the returned MODE SENSE data, at the Device's discretion. A DBD bit of one

specifies that the Device shall not return any block descriptors in the returned MODE SENSE data.

The page control (PC) field defines the type of parameter values to be returned. The page control field

is defined in Table 6-32

Table 6-32 Page Control Field

PC Value Type of Parameter Values

00b Current Values

01b Reserved

10b Reserved

11b Reserved

The page code specifies which page or pages to return. Page code usage is defined in Table 6-33.

Table 6-33 Page Code Usage for All Devices

Page Code Description

00h Vendor Specific (do not require page format)

01h - 1Fh See specific Device-types

20h - 3Eh Vendor Specific (page format required)

3Fh Return all pages

If a MODE SENSE command is attempted with a page code value not implemented, the Device shall

return “Check Condition” status and shall set the Sense Key to ILLEGAL REQUEST and the

Additional Sense Code to INVALID FIELD IN COMMAND PACKET.

A page code of 3Fh indicates that all pages implemented by the Device shall be returned. Page 00h, if

implemented, shall be returned after all other pages. Devices that implement more than 255 bytes of

mode page parameter data and block descriptors shall return “Check Condition” status to a MODE