TMS279X datasheet(2/40 Pages) TI

2 / 40 page

TMS279X (WD279X) FLOPPY DISK FORMATTER / CONTROLLER FAMILY

pin descriptions

NUMBER

PIN NAME

SYMBOL

FUNCTION

ENABLE PRECOMP

ENP

A Logic high on this input enables write precompensation to

be performed on double density Write Data output only.

MASTER RESET#

MR#

A logic low (50 microseconds min.) on this input resets the

device and loads HEX 03 into the command register. The Not

Ready (Status Bit 7) is reset during MR ACTIVE. When MR#

is brought to a logic high a RESTORE Command is executed,

regardless of the state of the Ready signal from the drive.

Also, HEX 01 is loaded into sector register.

POWER SUPPLIES

VSS

Ground

VCC

+5V ±5%

COMPUTER INERFACE

WRITE ENABLE#

WE#

A logic low on this input gates data on the DAL into the

selected register when CS# is low.

CHIP SELECT#

CS#

A logic low on this input selects the chip and enables

computer communication with the device.

READ ENABLE#

RE#

A logic low on this input controls the placement of data from a

selected register on the DAL when CS# is low.

5,6

LINE

A0, A1

These inputs select the register to receive / transfer data on

the DAL lines under RE# and WE# control:

CS#

RE#

Status Reg

Track Reg

Sector Reg

Data Reg

WE#

Command Reg

Track Reg

Sector Reg

Data Reg

7-14

DATA ACCESS LINES

DALO-

DAL7

Eight bit bi-directional bus used for transfer of commands,

status, and data. These lines are inverted (active low) on

TMS2791 and TMS2795.

CLOCK

CLK

This input requires a free-running 50% duty cycle square wave

clock for internal timing reference, 2 MHz ± 1 % for 8" drives, 1

MHz ± 1 % for mini-floppies.

DATA REQUEST

DRQ

This output indicates that the Data Register contains

assembled data in Read operations, or the DR is empty in

Write operations. This signal is reset when serviced by the

computer through reading or loading the DR.

INTERRUPT

REQUEST

INTRQ

This output is set at the completion of any command and is

reset when the Status register is read or the Command

FLOPPY DISK INTERFACE

STEP

The step output contains a pulse for each step.

DIRECTION

DIRC

Direction Output is active high when stepping in, active low

when stepping out.

5 1/4”, 8" SELECT

5#/8

This input selects the internal VCO frequency for use with

51/4" drives or 8" drives.

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