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12.4.1 Overview
This command enables the host to alter the device’s microcode. The data transferred using the Download Microcode
commands is vendor specific.
In reloading new microcode, when the spin-up of the device is disabled, the device spins down after reloading new
microcode.
The device may abort the Download Microcode command and discard all previously downloaded Microcode, if the
current buffer offset is not equal to the sum of the previous Download Microcode command buffer offset and the
previous sector count. The first Download Microcode command must have a buffer offset of zero. The new firmware
should become effective immediately after the transfer of the last data segment has completed.
When the device detects the last Download Microcode command for the firmware download the device performs any
device required verification and saves the complete set of downloaded microcode.
Power on reset prior to the receipt of the last segment will discard all of the microcode segments received.
This command is aborted when the device is in security locked mode
12.4.2 Sector Number / Sector Count
All transfers be an integer multiple of the sector size. The size of the data transfer is determined by the contents of
the Sector Number and Sector Count registers. The Sector Number register is used to extend the Sector Count
register to create a 16-bit sector count value. The Sector Number register is the most significant eight bits and the
Sector Count register is the least significant eight bits. A value of zero in both the Sector Number and Sector Count
registers indicate no data is to be transferred.
12.4.3 Download with offsets and save microcode
A Features register value of 03h indicates that the microcode will be transferred in one or more Download Microcode
commands using the offset transfer method. The buffer offset value is defined by the value in Cylinder registers. The
buffer offset value is the starting location in the microcode file, which varies in 512 byte increments. All microcode
segments will be sent to the device in sequence.
12.4.4 Download with offsets and save microcode for future use
A Features register value of 0Eh indicates that the microcode will be transferred in one or more Download Microcode
commands using the offset transfer method and stored for deferred update. The buffer offset value is defined by the
value in Cylinder registers. The buffer offset value is the starting location in the microcode file, which varies in 512
byte increments.
All microcode segments will be sent to the device in sequence.
12.4.5 Activate downloaded microcode
The device may abort the Download Microcode command and discard all previously downloaded Microcode, if the
current buffer offset is not equal to the sum of the previous Download Microcode command buffer offset and the
previous sector count. The first Download Microcode command must have a buffer offset of zero.
After the transfer of the last data segment has completed, the device performs any device required verification and
stores the complete set of downloaded microcode which has not been activated. The new firmware will be activated
after the device receives following Download Microcode command with a Features register value of 0Fh.
Power on reset prior to the receipt of the last segment or activate downloaded microcode will discard all of the
microcode segments which are received or stored.
12.4.6 Error Outputs
ABT will be set to 1 in the Error Register if the value in the Feature register is neither 03h, 07h, 0Eh nor 0Fh, or the
device is in Security Locked mode. When the reload of new microcode is requested in the data sent by the host for
this Download command, UNC error will be set to 1 in the Error Register if the device fails to reload new microcode.
This error is reported only when the reload of microcode is requested.
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Hard Disk Drive Specification