2/8 The Floppy Drive Roll call Video: floppy drive Step-by-step lecture

Watch the Video Two parts.

1: A floppy disk goes in The disk presses against a system of levers. One lever opens the shutter to expose the cookie. lever shutter

1A: What’s a cookie? The cookie is a piece of Mylar (plastic) with a magnetic coating on both sides.

2. The heads are positioned. Other levers and gears move the read/write heads into position, almost touching the cookie. Read/write heads

2A: The read/write heads. Electromagnets that can read or write data to the diskette.

3. Controlling movement: spin The shaft is run by the drive’s controller board. The shaft engages the disk’s hub via the notch to spin it. shaft notch in hub

4. Controlling moves: read/write heads The controller board runs a stepper motor, which rotates to slide the heads back and forth. Stepper motor

5. Reading from a diskette The diskette has magnetically coded data stored on it. Data is binary (1 or 0, on or off, north or south)

5A. Reading from a diskette The read/write heads are electromagnets. To read, the magnetic signal on the disk influences the core of the head. core coil

5B. Reading from a diskette The magnetic force creates a slight electric charge that travels up one of the two wires.

5C. Reading from a diskette The head moves to the next band. If the polarities match, the resulting bit is a 0. If it is opposite, it is a

5D. Reading from a diskette The next bit always starts with opposite polarity. 01 1st bit2nd bit 3rd bit 0

6. Writing to a diskette: can it be done? A diode and light sensor combo checks. If the light can pass, the disk cannot be written to. If it is blocked, the disk can be written to.

6A. Writing to a diskette Reverse the order to write to a diskette (wire - coil - core - disk ).

6B. Writing to a diskette Reverse the order to write to a diskette (wire - coil - core - disk ). Draw 1001 for a diskette st bit2nd bit3rd bit4th bit