Deskstar T7K500 Hard Disk Drive Specification
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12.18 Read Long (22h/23h)
Table 107: Read Long (22h/23h)
The Read Long command reads the designated one sector of data and the ECC bytes from the disk media. It then
transfers the data and ECC bytes from the device to the host.
After 512 bytes of data have been transferred, the device will keep setting DRQ = 1 to indicate that the device is
ready to transfer the ECC bytes to the host. The data is transferred 16 bits at a time and the ECC bytes are trans-
ferred 8 bits at a time. The number of ECC bytes are 4 or 40 according to the setting of Set Feature option. The
default setting is 4 bytes of ECC data.
The command makes a single attempt to read the data and does not check the data using ECC. Whatever is read is
returned to the host.
Output parameters to the device
Sector Count This indicates the number of continuous sectors to be transferred. The Sector Count must
be set to one.
Sector Number This indicates the sector number of the sector to be transferred. (L = 0)
In LBA mode, this register contains LBA bits 0–7. (L = 1)
Cylinder High/Low This indicates the cylinder number of the sector to be transferred. (L = 0)
In LBA mode, this register contains LBA bits 8–15 (Low), 16–23 (High). (L = 1)
H This indicates the head number of the sector to be transferred. (L = 0)
In LBA mode, this register contains LBA bits 24–27. (L = 1)
R This indicates the retry bit. This bit is ignored.
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 0 0 0 0 0 0 0 1 Sector Count - - - - - - - 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 1 R Status see below
Error Register Status Register
7654321 0 76543 21 0
CRC UNC 0 IDN 0 ABT T0N AMN BSY RDY DF DSC DRQ COR IDX ERR
000V0V0 0 0V0V- 0- V
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