FLOPPY DISK INTERFACE

Many mass storage devices like floppy disk drive,hard disk drive,optical drives like CD-ROM etc.

Drive unit is responsible for W/R data to/from storage medium.

Interface provides these devices to communicate with the system.

OVERVIEW

Fig.(a) Floppy disk

Interface consists of components like separate adapter card,separate controller.

The primary interfaces used in PCs today – Enhanced Integrated Drive Electronics(EIDE) & Small Computer Systems Interface(SCSI).

Besides EIDE & SCSI, most PCs have separate controller for floppy disk drives integrated into the motherboard.

When the hard disk drive came over,the floppy drive remained because it fulfill three important roles.

Booting the system Distributing software Providing removable storage

ROLES OF FLOPPY DRIVES

The floppy disk interface consists of three basic components :

The floppy drive controller The power cable The control/data cable

COMPONENTS OF INTERFACE

The FDC was a separate component in the form of an expansion card that plugged into the system’s Industry Standard Architecture (ISA) bus.

When there is a need for other drives such as hard drives etc requiring controllers then a separate controller card for each device came to become an impractical idea.

Until about 1994, FDC had been integrated into a multifunction card.

Today FDC is integrated into motherboard using super I/O chip

Function of super I/O chip – it strengthens the function of standard peripherals into one unit.

FLOPPY DRIVE CONTROLLER (FDC)

Fig(b) :The diagram below shows a fl oppy disc controller which communicates with the CPU via an

Industry Standard Architecture (ISA) bus.

The speed of the controller had to be increased in order to send data to the drive at the appropriate rate.

Higher capacity drivers require a controller with a faster transmission rate as the disk has higher bit density per track

The disk is storing more data,so the controller has to feed more data to the drive in the same amount of time.

FLOPPY CONTROLLER SPEEDS

Standard configuration for a FDC is to use IRQ6,Direct Memory Access,and I/O address 3F0-3F7h.

Should not change the resource allocation of FDC,if a new device is installing and it confl icts with the FDC change the configuration of the device and leave the FDC resources alone.

FLOPPY CONTROLLER RESOURCES

A FDD has two connections to the PC i.e.,a power cable & a control/data cable.

The power cable runs from the computer’s power supply to the drive,carries the power needed to run it.

Floppy disks requirs two voltages:+5.0V for the logic ckt and +12.0v for the motors.

FDD use 4 pin mate-n-lock connector which delivers both of these voltages plus a ground for each one.

POWER CABLE

The data cable has 34 pins,& diff erent connectors are designed to support the diff erent drive sizes.

Function – it carries dta b/w computer and the driveNew PCs off ers a two connector cable.A computer uses one cable for all the FDDs,& has two

connectors of each type to support any combination FDD.

B/w the two pairs of connectors for each drive there is a cutout that reverses the signals for pins 10 through 16 and used to diff erentiate the connectors.

CONTROL/DATA CABLE

Fig(c). The Floppy Drive control/data cable

All the odd numbered pins are grounds.Functionality of even numbered pins are as follows :- pin 2 – indicates whether the disk currently in drive

is normal or high density. pin 10 & 16 – signals the motors on each of the two

drives to increase the speed. pin 12 & 14 – indicate which drive should be

receiving & processing the incoming signals. pin 18 – controls the movement of the drive heads pin 20 – instructs the head to move a minute

distance. pin 22 & 30 – carries the actual data read/write

from/to the disk in the drive

FLOPPY CONTROL/DATA CABLE PINOUTS

Fig(d): Floppy disk data cable pin assignments

pin 24 – indicates whether the drive should be reading/writing.

pin 26 – indicates when the drive’s head are positioned over track 00 on the disk

pin 28 – specifies whether or not the disk is write protected

pin 32 – indicates which of the drive’s two heads is activated

pin 34 – used to signal the system that a new disk has been inserted into the drive

In data cable no 1 wire diff erent color(red) than other 33 wires so that it can be lined up with the pins on the motherboard.

The motherboard have one corner pin numbered as 1 and this pin goes into the side of cable connector with the coloured wire.

To connect cable to the drive attach one of the two connectors at the end of the cable opposite the motherboard connector.

CONNECTING THE DATA CABLE

There are many problems in interface components One of the problem caused by the interface is

“phantom drive”When there is a new disk in the drive and the OS

continues to display the fi les on the old disk. It is due to the disk change signal not arriving at the

controller over pin 34.

FLOPPY INTERFACE PROBLEMS

THANK YOU

Submitted By : HIMANSHI & BHARTI