SMC032BFY6 datasheet(68/91 Pages) STMICROELECTRONICS

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CF-ATA command description

SMCxxxBF

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10.11

Read Multiple (C4h)

The Read Multiple command performs similarly to the Read Sectors command. Interrupts

are not generated on every sector, but on the transfer of a block which contains the number

of sectors defined by a Set Multiple command.

Command execution is identical to the Read Sectors operation except that the number of

sectors defined by a Set Multiple command are transferred without intervening interrupts.

DRQ qualification of the transfer is required only at the start of the data block, not on each

sector.

The block count of sectors to be transferred without intervening interrupts is programmed by

the Set Multiple Mode command, which must be executed prior to the Read Multiple

command. When the Read Multiple command is issued, the Sector Count Register contains

the number of sectors (not the number of blocks or the block count) requested. If the number

of requested sectors is not evenly divisible by the block count, as many full blocks as

possible are transferred, followed by a final, partial block transfer. The partial block transfer

is for n sectors, where:

n = (sector count) module (block count).

If the Read Multiple command is attempted before the Set Multiple Mode command has

been executed or when Read Multiple commands are disabled, the Read Multiple operation

is rejected with an Aborted Command error. Disk errors encountered during Read Multiple

commands are posted at the beginning of the block or partial block transfer, but DRQ is still

set and the data transfer will take place as it normally would, including transfer of corrupted

data, if any.

Interrupts are generated when DRQ is set at the beginning of each block or partial block.

The error reporting is the same as that on a Read Sector(s) Command. 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

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.

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 which contained

the error.

Table 61 defines the Read Multiple command Byte sequence.

Table 61.

Read Multiple

Bit

432

Command (7)

C4h

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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