FDC37B80X View Datasheet(PDF) - SMSC -> Microchip

Part Name

Description

Manufacturer

FDC37B80X

PC98/99 compliant enhanced super I/O controller with Keyboard / Mouse Wake-Up / 5 Volt Operation

SMSC -> Microchip 

Configure

The Configure command is issued to select the

special features of the FDC. A Configure

command need not be issued if the default

values of the FDC meet the system

requirements.

Configure Default Values:

(765A). A value of 90 H is returned as the result

byte.

Relative Seek

The command is coded the same as for Seek,

except for the MSB of the first byte and the DIR

bit.

EIS - No Implied Seeks

EFIFO - FIFO Disabled

POLL - Polling Enabled

FIFOTHR - FIFO Threshold Set to 1 Byte

PRETRK - Pre-Compensation Set to Track 0

DIR

ACTION

0 Step Head Out

1 Step Head In

DIR Head Step Direction Control

EIS - Enable Implied Seek. When set to "1", the

FDC will perform a Seek operation before

executing a read or write command. Defaults to

no implied seek.

RCN

Relative Cylinder Number that

determines how many tracks to step the

head in or out from the current track

number.

EFIFO - A "1" disables the FIFO (default). This

means data transfers are asked for on a byte-

by-byte basis. Defaults to "1", FIFO disabled.

The threshold defaults to "1".

The Relative Seek command differs from the

Seek command in that it steps the head the

absolute number of tracks specified in the

command instead of making a comparison

POLL - Disable polling of the drives. Defaults to

"0", polling enabled. When enabled, a single

interrupt is generated after a reset. No polling is

performed while the drive head is loaded and

the head unload delay has not expired.

against an internal register. The Seek

command is good for drives that support a

maximum of 256 tracks. Relative Seeks cannot

be overlapped with other Relative Seeks. Only

one Relative Seek can be active at a time.

Relative Seeks may be overlapped with Seeks

FIFOTHR - The FIFO threshold in the execution

phase of read or write commands. This is

programmable from 1 to 16 bytes. Defaults to

and Recalibrates. Bit 4 of Status Register 0

(EC) will be set if Relative Seek attempts to step

outward beyond Track 0.

one byte. A "00" selects one byte; "0F" selects

16 bytes.

As an example, assume that a floppy drive has

300 useable tracks. The host needs to read

PRETRK - Pre-Compensation Start Track

Number. Programmable from track 0 to 255.

Defaults to track 0. A "00" selects track 0; "FF"

selects track 255.

track 300 and the head is on any track (0-255).

If a Seek command is issued, the head will stop

at track 255. If a Relative Seek command is

issued, the FDC will move the head the

specified number of tracks, regardless of the

Version

internal cylinder position register (but will

increment the register). If the head was on track

The Version command checks to see if the

controller is an enhanced type or the older type

40 (d), the maximum track that the FDC could

position the head on using Relative Seek will be

295 (D), the initial track + 255 (D). The

maximum count that the head can be moved

62

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