Hitachi hard disk drive specifications
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9.18.1.3 SCT Command Nesting and intermingling with Standard commands
In general, standard ATA commands can be intermingled with SCT Commands but SCT commands cannot be
nested. SCT commands that do not require a follow-on data transfer operation never have an issue with being
intermixed with any ATA commands or each other. SCT commands that do require data transfer, on the other
hand, may not be nested; that is, if a key command that requires a data transfer is issued, all data transfer - to or
from the host - must complete before another SCT command is issued. In most cases, however, ATA
read/write commands may be inserted in between SCT data transfers, that is, between complete SMART Read
Log/Write Log commands. Furthermore, any reset (power-on, software or hardware) will cause the SCT
command to be aborted.
9.18.1.4 Resets
In an SCT command is executing, any reset including Soft Reset, Hard Reset, COMRESET, and Power-On
Reset all cause the command to be terminated. This could result in partial command execution or data loss.
There is no indication once the drive becomes ready that the previous command was terminated.
9.18.2 SCT Command Protocol
9.18.2.1 Command Transport
SCT Command Transport occurs when a 512-byte data packet (called “Key Sector”) is created and the written to
SMART or extended log page E0h. The key sector specifies Action and Function Codes along with the
parameters that are required to perform the action.
9.18.2.1.1 Issue SCT Command Using SMART
Command Block Output Registers
Table 38 Output Registers of SCT Command Using SMART
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