Specifications

ATAPI For Streaming Tape QIC-157 Rev B

The page length field specifies the length in bytes of the following supported page list,

The supported page list field shall contain a list of all log page codes implemented by the Device in

ascending order beginning with page code 00h.

6.8.6.38.Error Counter Pages Codes 02, 03

This section defines the optional error counter pages for write errors (page code 02h), and read errors

(page code 03h). Table 6-23 defines the page format for these pages. A page can return one or more

log parameters which record events defined by the parameter codes.

[Implementor's Note: Devices shall only reset its error counters at power-on or on command from the Host. Table 6-25

defines the parameter codes for the error counter pages. Support of each log parameter is optional.]

Table 6-25 Parameter Codes for Error Counter Pages

Parameter Code Description

0000h Errors corrected on-the-fly

0001h Errors corrected by other means

0002-7FFFh Reserved

8000h-8003h Reserved

8004-FFFFh Vendor specific

6.8.6.38.1.Error Counter Page (Read)

This section defines the parameter codes for the Error Counter Page (Read), page code 03h. Table 6-

26 defines the counters and their use.

The following techniques can be used to attempt to recover bad blocks when reading from tape.

1. ECC. An ECC algorithm is applied to the data blocks and parity blocks within a frame in order to

correct the bad blocks. This technique can only be used when a minimum number of bad blocks

are detected in a frame.

2. Tape re-positions. The tape is re-positioned so that the frame read operation can be repeated.

3. Head adjustments. The head position in relation to the track is slightly modified. Head adjustments

are done in combination with tape re-positions.

4. Signal threshold changes. The read amplitude dc values are modified slightly to capture more

signal transitions. Signal threshold changes are made in combination with tape re-positions.

Table 6-26 Parameter Codes for Error Counter Page (Read) - Page Code 03h

Code Description

0000h Number of blocks recovered by ECC alone.

0001h Number of blocks recovered without using ECC. This count is incremented when blocks are recovered

due to:

- tape re-positioning alone

- combination of tape re-positioning and head adjustments

- combination of tape re-positioning and signal threshold changes.

However, no additional ECC processing is required.

Implementor's Note:

1. The term "blocks" refers to physical blocks on tape.

2. A block read error is only counted as being in error on the first attempt to read the block.