User Manual

ATA Command Description

5-12 CompactFlash

Subsequent blocks or partial blocks are transferred only if the error was a correctable data error. All other errors

cause the command to stop after transfer of the block that contained the error.

5.1.11. Read Long Sector—22H, 23H

Table 5-14. Read Long Sector

Bit -> 7 6 5 4 3 2 1 0

Command (7) 22H or 23H

C/D/H (6) 1 LBA 1 Drive Head (LBA 27-24)

Cyl High (5) Cylinder High (LBA 23-16)

Cyl Low (4) Cylinder Low (LBA 15-8)

Sec Num (3) Sector Number (LBA 7-0)

Sec Cnt (2) X

Feature (1) X

The Read Long command performs similarly to the Read Sector(s) command except that it returns 516 bytes of data

instead of 512 bytes. During a Read Long command, the CompactFlash Memory Card does not check the ECC bytes

to determine if there has been a data error. Only single sector read long operations are supported. The transfer

consists of 512 bytes of data transferred in word mode followed by 4 bytes of random data transferred in byte mode.

Random data is returned instead of ECC bytes because of the nature of the ECC system used. This command has the

same protocol as the Read Sector(s) command.

5.1.12. Read Sector(s)—20H, 21H

Table 5-15. Read Sectors

Bit -> 7 6 5 4 3 2 1 0

Command (7) 20H or 21H

C/D/H (6) 1 LBA 1 Drive Head (LBA 27-24)

Cyl High (5) Cylinder High (LBA 23-16)

Cyl Low (4) Cylinder Low (LBA 15-8)

Sec Num (3) Sector Number (LBA 7-0)

Sec Cnt (2) Sector Count

Feature (1) X

This command reads from 1 to 256 sectors as specified in the Sector Count register. A sector count of 0 requests 256

sectors. The transfer begins at the sector specified in the Sector Number Register. When this command is issued and

after each sector of data (except the last one) has been read by the host, the CompactFlash Memory Card sets BSY,

puts the sector of data in the buffer, sets DRQ, clears BSY, and generates an interrupt. The host then reads the 512

bytes of data from the buffer.

At command completion, the Command Block Registers contain the cylinder, head and sector number of the last

sector read. If an error occurs, the read terminates at the sector where the error occurred. The Command Block

Registers contain the cylinder, head, and sector number of the sector where the error occurred. The flawed data is

pending in the sector buffer.