LPC47M172 datasheet(63/227 Pages) SMSC

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Advanced I/O Controller with Motherboard GLUE Logic

Datasheet

SMSC/Non-SMSC Register Sets (Rev. 02-27-04)

Page 63

SMSC LPC47M172

DATASHEET

6.11

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

status normally returned for a Read/Write Data command. Status Register 0 (ST0) would contain the error

code and C would contain the cylinder on which the seek failed.

6.11.1 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 is 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 the TC cycle, 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 6.18 below). If N is set to zero, the sector size is

set to 128. The DTL value determines the number of bytes to be 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 6.18 - Sector Sizes

SECTOR SIZE

128 bytes

256 bytes

512 bytes

1024 bytes

…

16 Kbytes

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 6.19.

LPC47M172 Datasheet(PDF) 63 Page - SMSC Corporation

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