Hitachi HCS721075CLA332, HCS721050CLA382, HCS721032CLA382, A7K2000 12 48-bit Address Feature Set

9.1248-bit Address Feature Set

The 48-bit Address feature set allows devices with capacities up to 281,474,976,710,655 sectors. This allows device capacity up to 144,115,188,075,855,360 bytes. In addition, the number of sectors that may be transferred by a single command are increased by increasing the allowable sector count to 16 bits.

Commands unique to the 48-bit Address feature set are:

Flush Cache Ext

Read DMA Ext

Read FPDMA Queued

Read Multiple Ext

Read Native Max Address Ext

Read Sector(s) Ext

Read Verify Sector(s) Ext

Set Max Address Ext

Write DMA Ext

Write DMA FUA Ext

Write FPDMA Queued

Write Multiple Ext

Write Multiple FUA Ext

Write Sector(s) Ext

Write Uncorrectable Ext

The 48-bit Address feature set operates in LBA addressing only. Devices also implement commands using 28-bit addressing, and 28-bit and 48-bit commands may be intermixed.

In a device, the Features, the Sector Count, the Sector Number, the Cylinder High, and the Cylinder Low registers are a two-byte-deep FIFO. Each time one of these registers is written, the new content written is placed into the "most recently written" location and the previous content is moved to "previous content" location.

The host may read the "previous content" of the Features, the Sector Count, the Sector Number, the Cylinder High, and the Cylinder Low registers by first setting the High Order Bit (HOB, bit 7) of the Device control register to one and then reading the desired register. If HOB in the Device Control register is cleared to zero, the host reads the "most recently written" content when the register is read. A write to any Command Block register shall cause the device to clear the HOB bit to zero in the Device Control register. The "most recently written" content always gets written by a register write regardless of the state of HOB in the Device Control register.

Support of the 48-bit Address feature set is indicated in the Identify Device response bit 10 word 83. In addition, the maximum user LBA address accessible by 48-bit addressable commands is contained in Identify Device response words 100 through 103.

When the 48-bit Address feature set is implemented, the native maximum address is the value returned by a Read Native Max Address Ext command. If the native maximum address is equal to or less than 268,435,455, a Read Native Max Address shall return the native maximum address. If the native maximum address is greater than 268,435,455, a Read Native Max Address shall return a value of 268,435,455.

Hitachi hard disk drive specifications

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