Hitachi HDS723020BLA642 Specifications page 119

Number and Sector Count registers shall indicate no data is to be transferred.
ABT will be set to 1 in the Error Register if the value in the Feature register is neither 03h nor 07h, 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.
In reloading new microcode, when the spin-up of the device is disabled, the device spins down after reloading
new microcode.
A Features register value of 03h indicates that the microcode will be transferred in two 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 shall be sent to the device in sequence.
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 shall
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 shall
perform any device required verification and save the complete set of downloaded microcode.
If the device receives a command other than download microcode prior to the receipt of the last segment the
new command is executed and all previously downloaded microcode is discarded.
If a software or hardware Reset is issued to the device before all of the microcode segments have been
transferred to the device the device shall abandon all of the microcode segments received and process the
Reset.
Hitachi hard disk drive specifications
119