SMCXXXBF datasheet(69/91 Pages) STMICROELECTRONICS

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SMCxxxBF

CF-ATA command description

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10.12

Read Sector(s) (20h or 21h)

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 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.

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 are pending in the sector buffer. Table 62 defines

the Read Sector command Byte sequence.

10.13

Read Verify Sector(s) (40h or 41h)

This command is identical to the Read Sectors command, except that DRQ is never set and

no data is transferred to the host. When the command is accepted, the Card sets BSY.

When the requested sectors have been verified, the Card clears BSY and generates an

interrupt.

If an error occurs, the verify terminates at the sector where the error occurs. The Command

Block Registers contain the cylinder, head and sector number of the sector where the error

occurred. The Sector Count Register contains the number of sectors not yet verified.

Table 63 defines the Read Verify Sector command Byte sequence.

Table 62.

Read Sector(s)

Bit

765

Command

(7)

20h or 21h

C/D/H (6)

LBA

Drive

Head (LBA 27-24)

Cyl High

(5)

Cylinder High (LBA 23-16)

Cyl Low (4)

Cylinder Low (LBA 15-8)

Sect Num

(3)

Sector Number (LBA 7-0)

Sect Cnt

(2)

Sector Count

Feature (1)

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