TMS279X datasheet(3/40 Pages) TI

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TMS279X (WD279X) FLOPPY DISK FORMATTER / CONTROLLER FAMILY

NUMBER

PIN NAME

SYMBOL

FUNCTION

READ PULSE WIDTH

RPW

An external potentiometer tied to this input controls the phase

comparator within the data separator.

TEST#

A logic low on this input allows adjustment of external resistors

by enabling internal signals to appear on selected pins.

PUMP

High-Impedance output signal which is forced high or low to

increase / decrease the VCO frequency

ENABLE

MINI-FLOPPY

(2791,2793)

ENMF#

A logic low on this input enables an internal divide by 2 of the

Master Clock. This allows both 51/4" and 8" drive operation with

a single 2 MHz clock. For a 1 MHz clock on Pin 24, this line

must be left open or tied to a Logic 1.

SIDE SELECT

OUTPUT

(2795,2797)

SSO

The logic level of the Side Select Output is directly controlled by

the 'S' flag in Type 11 or III commands. When U = 1, SSO is set

to a logic 1. When U = 0, SSO is set to a logic 0. The SSO is

compared with the compare Status Bit 4 (RNF) is set. The Side

Select Output is only updated at the beginning of a Type II or III

command. It is forced to a logic 0 upon a MASTER RESET

condition.

VOLTAGE-

CONTROLLED

OSCILLATOR

VCO

An external capacitor tied to this pin adjusts the VCO center

frequency

RAW READ#

RAW RD#

The data input signal directly from the drive. This input shall be

a negative pulse for each recorded flux transition.

HEAD LOAD

HLD

The HLD output controls the loading of the Read- Write head

against the media.

TRACK GREATER

THAN 43

TG43

This output informs the drive that the Read/Write head is

positioned between tracks 44-76. This output is valid only

during Read and Write Commands.

WRITE GATE

This output is made valid before writing is to be performed on

the diskette.

WRITE DATA

MFM or FM output pulse per flux transition. WD contains the

unique Address marks as well as data and clock in both FM and

MFM formats.

READY

This input indicates disk readiness and is sampled for a logic

high before Read or Write commands are performed. If Ready

is low the Read or Write operation is not performed and an

interrupt is generated. Type I operations are performed

regardless of the state of Ready. The Ready input appears in

inverted format as Status Register bit 7.

WRITE PRECOMP

WIDTH

WPW

An external potentiometer tied to this input controls the amount

of delay in Write precompensation mode.

TRACK 00#

TR00#

This input informs the TMS279X that the Read/Write head is

positioned over Track 00.

INDEX PULSE#

IP#

This input informs the TMS279X when the index hole is

encountered on the diskette.

WRITE PROTECT#

WPRT#

This input is sampled whenever a Write Command is received.

A logic low terminates the command and sets the Write Protect

Status bit.

NOTE: A trailing # replaces the overbar means the symbol is active low.

TMS279X Datasheet(PDF) 3 Page - Texas Instruments

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