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Western Digital Hard Disk Drive OEM Specification
11.6 Execute Device Diagnostic (90h)
Command Block Output Registers
Command Block Input Registers
Table 107 Execute Device Diagnostic Command (90h)
The Execute Device Diagnostic command performs the internal diagnostic tests implemented by the device. The
results of the test are stored in the Error Register.
The normal Error Register bit definitions do not apply to this command. Instead, the register contains a diagnostic
code. See Table 34 Diagnostic Codes on the page 42 for its definition.