360050398

10.8.5 Read Sector

(20h/21h)

 

 

 

 

 

 

 

COMMAND CODE

0 0 1 0 0 0 0 X

REGISTER

 

 

REGISTER SETTING

NORMAL COMPLETION

 

DR

 

drive no.

no change

 

CY

 

starting cylinder

last possible

 

HD

 

starting head

last possible

 

SN

 

starting sector

last possible

 

SC

 

no. of sector to read

00H

 

FT

 

 

 

no change

 

LBA

 

staring address

last address

Setting BSY bit, the drive will seek to the target cylinder if the head is not on target track ( implied seek ), select the head and begin to read the number of sector defined in SC register ( 1-256 ) starting from the target sector. After finding ID of target sector and having 1 sector of data read into the buffer RAM, the drive sets DRQ in status register and generates interrupt to report to the host that the drive is ready to transfer the next data.

In case of multi-sector transfer, DRQ bit is reset and BSY is set after 1 sector transfer to prepare for the next sector transfer.

An uncorrectable data can also be transferred but the subsequent operation will terminate at the cylinder, head, and sector (or LBA) position in the TASK FILE register. When a sector is ready to be read by the host, an interrupt is issued. After the last sector is read by the host, no interrupt is issued at the end of a command.

10.8.6 Read Sector EXT

(24h)

 

 

 

 

 

 

 

 

 

 

 

 

COMMAND CODE

0 0 1 0 0 1 0 0

 

REGISTER

 

 

 

 

REGISTER SETTING

NORMAL COMPLETION

 

DR

 

 

drive no.

 

no change

 

LBA

Current

 

LBA(7:0)

HOB=0

 

last address

 

 

 

 

Low

Previous

 

LBA(31:24)

HOB=1

 

last address

 

LBA

Current

 

LBA(15:8)

HOB=0

 

last address

 

Mid

Previous

 

LBA(39:32)

HOB=1

 

last address

 

LBA

Current

 

LBA(23:16)

HOB=0

 

last address

 

High

Previous

 

LBA(47:40)

HOB=1

 

last address

 

SC

Current

 

sector count(7:0)

HOB=0

 

00H

 

 

Previous

 

sector count(15:8)

HOB=1

 

00H

 

FT

Current

 

reserved

HOB=0

 

no change

 

 

Previous

 

reserved

HOB=1

 

no change

Setting BSY bit, the drive will seek to the target cylinder if the head is not on target track ( implied seek ), select the head and begin to read the number of sector defined in SC register ( 1-65536 ) starting from the target sector. After finding ID of target sector and having 1 sector of data read into the buffer RAM, the drive sets DRQ in status register and generates interrupt to report to the host that the drive is ready to transfer the next data.

In case of multi-sector transfer, DRQ bit is reset and BSY is set after 1 sector transfer to prepare for the next sector transfer.

An uncorrectable data can also be transferred but the subsequent operation will terminate at the LBA position in the TASK FILE register. When a sector is ready to be read by the host, an interrupt is issued. After the last sector is read by the host, no interrupt is issued at the end of a command.

This command is available in LBA addressing only.

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