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Command Processing
2.8.3 Reserved operation code
Group 6, 7 command operation codes (X'C0' ~ X'FF') are reserved by Fujitsu.
When any command which has these operation codes is issued, the IDD may not
necessarily respond with the CHECK CONDITION status (ILLEGAL REQUEST
[= 5] Invalid command operation code [= 20-00]).
The INIT must not issue commands which have these operation codes.
2.8.4 Error recovery processing
When an error which it is possible to retry is detected in the IDD, the IDD
attempts error recovery processing of the detected error during command
execution.
The INIT can specify whether or not to report detailed parameters and
successfully recovered errors related to error recovery processing using either the
MODE SELECT or the MODE SELECT EXTENDED command. Also, by the
INIT specifying those parameters, they can be saved in the system space on the
disk medium and they can be changed temporarily without being saved. After the
power is turned on, or after reset, the IDD reads out the saved parameters and
initializes the error recovery processing procedure.
See Chapter 4, "Command Specifications" concerning details of the MODE
SELECT and MODE SELECT EXTENDED commands.
An outline of the error recovery processing executed by the IDD is shown below.
(1) Recovery procedures for disk drive errors
The IDD executes error recovery processing like that shown in Table 2.8 for errors
detected during data access on the disk medium. Caution is necessary when
performing these recovery processing procedures, because they are accompanied by
rotational delays for repositioning data blocks on the disk medium or by added
command processing time due to initialization of the positioning control system, etc.
The INIT can control the number of retries by page 1 (Read/Write error recovery
parameters), page 7 (Verify error recovery parameters) or page 21 (Additional
error recovery parameters) of the MODE SELECT parameters, but during normal
use, it is recommended that the default values specified by the IDD be used.
Table 2.8 Outline of disk drive error recovery processing
Item
Type of Error
1
Seek Error
2
Uncorrectable Data Error
3
Correctable Data Error
2-16
Error Recovery Processing
Rezero (Return to Zero Cylinder), readjustment of positioning
control system, and repositioning to the data block.
Reread
Correct by ECC.
C141-C012
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