Deskstar T7K250 Hard Disk Drive Specification
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12.24 Read Sectors (20h/21h)
Table 101: Read Sectors Command (20h/21h)
The Read Sectors command reads one or more sectors of data from disk media and then transfers the data from the
device to the host.
The sectors are transferred through the Data Register 16 bits at a time.
If an uncorrectable error occurs the read will be terminated at the failing sector.
Output parameters to the device
Sector Count This indicates the number of continuous sectors to be transferred. If zero is specified,
256 sectors will be transferred.
Sector Number This is the sector number of the first sector to be transferred. (L =0)
In LBA mode this register contains the LBA bits 0–7. (L = 1)
Cylinder High/Low This is the cylinder number of the first sector to be transferred. (L = 0)
In LBA mode this register contains the LBA bits 8–15 (Low) and bits 16–23 (High).
(L = 1)
H This is the head number of the first sector to be transferred. (L = 0)
In LBA mode this register contains the LBA bits 24–27. (L = 1)
R This is the retry bit, but this bit is ignored.
Input parameters from the device
Sector Count This is the number of requested sectors not transferred. This will be zero, unless an unre-
coverable error occurs.
Sector Number This is the sector number of the last transferred sector. (L = 0)
In LBA mode this register contains the current LBA bits 0–7. (L = 1)
Command Block Output Registers Command Block Input Registers
Register 7 6 5 4 3 2 1 0 Register 7 6 5 4 3 2 1 0
Data - - - - - - - - Data - - - - - - - -
Feature - - - - - - - - Error see below
Sector Count V V V V V V V V Sector Count V V V V V V V V
Sector Number V V V V V V V V Sector Number V V V V V V V V
Cylinder Low V V V V V V V V Cylinder Low V V V V V V V V
Cylinder High V V V V V V V V Cylinder High V V V V V V V V
Device/Head 1 L 1 D H H H H Device/Head - - - - H H H H
Command 0 0 1 0 0 0 0 R Status see below
Error Register Status Register
7654321 0 7654 3 21 0
CRC UNC 0 IDN 0 ABT T0N AMN BSY RDY DF DSC DRQ COR IDX ERR
0V0V0V0 V 0V0V - 0- V
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