Floppy drives are just dumb devices that are more or less able to:
- Give their ID (very simple logic does this)
- Spin a disk (drive motor on/off)
- Detect the correct spin speed (it is normally fixed, so no real detection involved)
- Detect disk change
- Detect write protection status
- Seek head in and out
- Select side
- Detect track 0, so software and firmware knows where the head is, and can then seek in any direction once the track 0 signal is detected
- Read the signal present at the current head position
- Write a signal to disk at the current head position
As you can see there is no logic, software or firmware whatsoever present in the base setup of a floppy disk drive. There is no “protocol” like in more modern devices (IDE, SCSI, USB, Firewire) It is pretty much a simple electromechanical device and as such, no error detection (or anything else) is done. This is why it is called a “legacy” device, it is dumb and needs special control, just like the serial and parallel ports do.
Of course, you can get USB floppy drives. They are certainly not dumb devices. They do have the same basic drive mechanics, but they are more like hard disks in that you have the electromechanical parts and you have the circuitry to control them on the same device. The computer only talks the USB protocol, not FDC (Floppy Disk Controller) commands. As you probably guessed, what actually makes USB drives different is that they have an onboard FDC. This, combined with their low volume manufacture, is why they are so much more expensive [Update: Now much less since this was originally written].
A normal PC drive setup can be represented as the following:
PC (including onboard FDC) <--> Drive Mechanics
In contrast, for USB drives it is more like the following:
PC (with USB Controller) <--> Floppy Device USB Controller
Inside that USB floppy you have the important stuff:
USB Controller <--> Control Hardware <--> FDC <--> Drive Mechanics
The FDC is the same type they put in PC’s and as such, it has very restrictive use. In fact, you probably have even less control than your common PC floppy drive since you do not talk FDC commands, you talk USB protocol.