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
Interface provides these
devices to communicate
with the system.
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
When the hard disk drive came over,the floppy
drive remained because it fulfill three
Booting the system
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
Until about 1994, FDC had been integrated into a
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)
shows a floppy
with the CPU
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 conflicts with the FDC change the
configuration of the device and leave the FDC resources
FLOPPY CONTROLLER RESOURCES
A FDD has two connections to the PC i.e.,a power cable & a
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.
The data cable has 34 pins,& different connectors are
designed to support the different drive sizes.
Function – it carries dta b/w computer and the drive
New PCs offers 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 differentiate the connectors.
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
pin 24 – indicates whether the drive should be
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 different color(red) than other 33
wires so that it can be lined up with the pins on the
The motherboard have one corner pin numbered as 1 and this
pin goes into the side of cable connector with the coloured
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 files on the old disk.
It is due to the disk change signal not arriving at the
controller over pin 34.
FLOPPY INTERFACE PROBLEMS