LPC47M192 datasheet(45/228 Pages) SMSC

45 / 228 page

SMSC DS – LPC47M192

Page 45

Rev. 03/30/05

DATASHEET

Data Transfer Termination

The FDC supports terminal count explicitly through the TC pin and implicitly through the underrun/overrun and end-

of-track (EOT) functions. For full sector transfers, the EOT parameter can define the last sector to be transferred in

a single or multi-sector transfer.

If the last sector to be transferred is a partial sector, the host can stop transferring the data in mid-sector, and the

FDC will continue to complete the sector as if a TC cycle was received. The only difference between these implicit

functions and TC cycle is that they return “abnormal termination” result status. Such status indications can be

ignored if they were expected.

Note that when the host is sending data to the FIFO of the FDC, the internal sector count will be complete when the

FDC reads the last byte from its side of the FIFO. There may be a delay in the removal of the transfer request signal

of up to the time taken for the FDC to read the last 16 bytes from the FIFO. The host must tolerate this delay.

Result Phase

The generation of the interrupt determines the beginning of the result phase. For each of the commands, a defined

set of result bytes has to be read from the FDC before the result phase is complete. These bytes of data must be

read out for another command to start.

RQM and DIO must both equal “1” before the result bytes may be read. After all the result bytes have been read, the

RQM and DIO bits switch to “1” and “0” respectively, and the CB bit is cleared, indicating that the FDC is ready to

accept the next command.

Command Set/Descriptions

Commands can be written whenever the FDC is in the command phase. Each command has a unique set of needed

parameters and status results. The FDC checks to see that the first byte is a valid command and, if valid, proceeds

with the command. If it is invalid, an interrupt is issued. The user sends a Sense Interrupt Status command which

returns an invalid command error. Refer to Table 16 for explanations of the various symbols used. Table 17 lists the

required parameters and the results associated with each command that the FDC is capable of performing.

Table 16 – Description of Command Symbols

SYMBOL

NAME

DESCRIPTION

Cylinder Address

The currently selected address; 0 to 255.

Data Pattern

The pattern to be written in each sector data field during formatting.

D0, D1

Drive Select 0-1

Designates which drives are perpendicular drives on the

Perpendicular Mode Command.

A “1” indicates a perpendicular

drive.

DIR

Direction Control

If this bit is 0, then the head will step out from the spindle during a

relative seek. If set to a 1, the head will step in toward the spindle.

DS0, DS1

Disk Drive Select

DS1

DS0

DRIVE

Drive 0

Drive 1

DTL

Special Sector

Size

By setting N to zero (00), DTL may be used to control the number of

bytes transferred in disk read/write commands. The sector size (N =

0) is set to 128. If the actual sector (on the diskette) is larger than

DTL, the remainder of the actual sector is read but is not passed to

the host during read commands; during write commands, the

remainder of the actual sector is written with all zero bytes. The CRC

check code is calculated with the actual sector. When N is not zero,

DTL has no meaning and should be set to FF HEX.

Enable Count

When this bit is “1” the “DTL” parameter of the Verify command

becomes SC (number of sectors per track).

EFIFO

Enable FIFO

This active low bit when a 0, enables the FIFO. A “1” disables the

FIFO (default).

EIS

Enable Implied

Seek

When set, a seek operation will be performed before executing any

read or write command that requires the C parameter in the

command phase. A “0” disables the implied seek.

EOT

End of Track

The final sector number of the current track.

LPC47M192 Datasheet(PDF) 45 Page - SMSC Corporation

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