FDC37M607 datasheet(52/182 Pages) SMSC

52 / 182 page

DATA TRANSFER COMMANDS

All of the Read Data, Write Data and Verify type

commands use the same parameter bytes and

return the same results information, the only

difference being the coding of bits 0-4 in the first

byte.

An implied seek will be executed if the feature

was enabled by the Configure command. This

seek is completely transparent to the user. The

Drive Busy bit for the drive will go active in the

Main Status Register during the seek portion of

the command.

If the seek portion fails, it is

reflected in the results status normally returned

for

Read/Write

Data

command.

Status

and C would contain the cylinder on which the

seek failed.

Read Data

A set of nine (9) bytes is required to place the

FDC in the Read Data Mode.

After the Read

Data command has been issued, the FDC loads

the head (if it is in the unloaded state), waits the

specified head settling time (defined in the

Specify command), and begins reading ID

Address Marks and ID fields. When the sector

address read off the diskette matches with the

sector address specified in the command, the

FDC reads the sector's data field and transfers

the data to the FIFO.

After completion of the read operation from the

current

sector,

the

sector

address

incremented by one and the data from the next

logical sector is read and output via the FIFO.

This continuous read function is called "Multi-

Sector Read Operation". Upon receipt of TC, or

an implied TC (FIFO overrun/underrun), the

FDC stops sending data but will continue to

read data from the current sector, check the

CRC bytes, and at the end of the sector,

terminate the Read Data Command.

N determines the number of bytes per sector

(see Table 21 below). If N is set to zero, the

sector size is set to 128. The DTL value

determines

the

number

bytes

transferred.

If DTL is less than 128, the FDC

transfers the specified number of bytes to the

host. For reads, it continues to read the entire

128-byte sector and checks for CRC errors. For

writes, it completes the 128-byte sector by filling

in zeros. If N is not set to 00 Hex, DTL should

be set to FF Hex and has no impact on the

number of bytes transferred.

Table 21 - Sector Sizes

The amount of data which can be handled with

a single command to the FDC depends upon

MT (multi-track) and N (number of bytes/sector).

The Multi-Track function (MT) allows the FDC to

read data from both sides of the diskette. For a

particular cylinder, data will be transferred

starting at Sector 1, Side 0 and completing the

last sector of the same track at Side 1.

If the host terminates a read or write operation

in the FDC, the ID information in the result

phase is dependent upon the state of the MT bit

and EOT byte. Refer to Table 22.

At the completion of the Read Data command,

the head is not unloaded until after the Head

Unload Time Interval (specified in the Specify

command) has elapsed.

If the host issues

another command before the head unloads,

SECTOR SIZE

128 bytes

256 bytes

512 bytes

1024 bytes

...

16 Kbytes

FDC37M607 Datasheet(PDF) 52 Page - SMSC Corporation

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