Deskstar 7K500 and Deskstar E7K500 Hard Disk Drive Specification
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10.3  Diagnostic and Reset considerations
For each Reset and Execute Device Diagnostic, the diagnostic is done as follows:
In all the above cases – Power On Reset, Soft Reset, and the Execute Device Diagnostic command – the Device 0 
Error register value is interpreted using the table below.
The "x" indicates the appropriate Diagnostic Code for the Power on, RESET-, Soft Reset, or Device Diagnostic 
error.
Power On Reset DASP– is read by Device 0 to determine if Device 1 is present. If Device 1 is present, 
Device 0 shall read PDIAG– to determine when it is valid to clear the BSY bit and 
whether Device 1 has powered on or reset without error, otherwise Device 0 clears the 
BSY bit whenever it is ready to accept commands. Device 0 may assert DASP– to 
indicate device activity. 
Hard Reset,
Soft Reset
If Device 1 is present, Device 0 shall read PDIAG– to determine when it is valid to clear 
the BSY bit and whether Device 1 has reset without any errors; otherwise, Device 0 shall 
simply reset and clear the BSY bit. DASP– is asserted by Device 0 (and Device 1 if it is 
present) in order to indicate device active.
Execute Device 
Diagnostic
If Device 1 is present, Device 0 shall read PDIAG– to determine when it is valid to clear 
the BSY bit and if Device 1 passed or failed the EXECUTE DEVICE DIAGNOSTIC 
command; otherwise, Device 0 shall simply execute its diagnostics and then clear the 
BSY bit. DASP– is asserted by Device 0 (and Device 1 if it is present) in order to 
indicate that the device is active.
Table 68: Reset error register values
Device 1 present?  PDIAG- Asserted? Device 0 Passed Error Register
Yes Yes Yes 01h
Yes Yes No 0xh
Yes No Yes 81h
Yes No No 8xh
No (not read) Yes 01h
No (not read) No 0xh