Fujitsu MBA3300RC, MBC2036RC, MBC2073RC Reserved operation code, Error recovery processing

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 HDD 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 HDD, the HDD 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 HDD 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 HDD is shown below.

(1) Recovery procedures for disk drive errors

The HDD 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 HDD be used.

Table 2.8 Outline of disk drive error recovery processing

Item	Type of Error	Error Recovery Processing
1	Seek Error	Rezero (Return to Zero Cylinder), readjustment of positioning
		control system, and repositioning to the data block.
2	Uncorrectable Data Error	Reread
3	Correctable Data Error	Correct by ECC.

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