PC87311A datasheet(74/78 Pages) NSC

74 / 78 page

100 Reference

101 MNEMONIC DEFINITIONS FOR FDC COMMANDS

Symbol

Description

BFR

Buffer enable bit used in the Mode command

Enabled open-collector output buffers

BST

Burst Mode disable control bit used in Mode

command Selects the Non-Burst FIFO mode if

the FIFO is enabled

DC0

Drive Configuration 0 – 3 Used to set DC1a

drive to conventional or perdendicular DC2

mode Used in Perpendicular Mode DC3 com-

mand

DENSEL

Density Select control bits used in the Mode

command

DIR

Direction control bit used in Relative Seek

command to indicate step in or out

DMA

DMA mode enable bit used in the Specify com-

mand

DR0

Drive Select 0 – 1 bits used in most commands

Selects the logical drive

DTL

Data Length parameter used in the Read

Write Scan and Verify commands

Enable Count control bit used in the Verify

command When this bit is 1 the DTL parame-

ter becomes SC (Sector Count)

EIS

Enable Implied Seeks Used in the Configure

command

EOT

End of Track parameter set in the Read Write

Scan and Verify commands

ETR

Extended Track Range used with the Seek

command

FIFO

First-In First-Out buffer Also a control bit used

in the Configure command to enable or disable

the FIFO

FRD

FIFO Read disable control bit used in the

Mode command

FWR

FIFO Write disable control bit used in the

Mode command

GAP

GAP2 control bit used in the Perpendicular

Mode command

Head Select control bit used in most com-

mands Selects Head 0 or 1 of the disk

IAF

Index Address Field control bit used in the

Mode command Enables the ISO Format dur-

ing the Format command

IPS

Implied Seek enable bit used in the Mode

Read Write and Scan commands

LOCK

Lock enable bit in the Lock command Used to

make certain parameters unaffected by a soft-

ware reset

LOW PWR

Low Power control bits used in the Mode com-

mand

MFM

Modified Frequency Modulation control bit

used in the Read Write Format Scan and

Verify commands Selects MFM or FM data

encoding

MFT

Motor Off Time programmed in the Specify

command

MNT

Motor On Time programmed in the Specify

command

Multi-Track enable bit used in the Read Write

Scan and Verify commands

Overwrite control bit used in the Perpendicular

Mode command

POLL

Enable Drive Polling bit used in the Configure

command

PRETRK

Precompensation Track Number used in the

Configure command

PTR

Present Track Register Contains the internal

track number for one of the four logical disk

drives

Pump diagnostic enable bit used in the Mode

command

R255

Recalibrate control bit used in Mode com-

mand Sets maximum recalibrate step pulses

to 255

Read Gate diagnostic enable bit used in the

Mode command

RTN

Relative Track Number used in the Relative

Seek command

Sector Count control bit used in the Verify

command

Skip control bit used in read and scan opera-

tions

SRT

Step Rate Time programmed in the Specify

command Determines the time between step

pulses for seek and recalibrates

ST0

Status Register 0 – 3 Contains status ST1 in-

formation about the execution of a ST2 com-

mand Read in the Result Phase of ST3 some

commands

THRESH

FIFO threshold parameter used in the Config-

ure command

TMR

Timer control bit used in the Mode command

Affects the timers set in the Specify command

Write Gate control bit used in the Perpendicu-

lar Mode command

WLD

Wildcard bit in the Mode command used to en-

able or disable the wildcard byte (FF) during

Scan commands

PC87311A Datasheet(PDF) 74 Page - National Semiconductor (TI)

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