External Floppy Disk Drive Will Not Reading Diskettes

Circuitry that controls reading from and writing to a computer's floppy disk drive

"3-mode" redirects here. For the logic, see 3-state.

v-ane/four Diskette Drive Adapter found on the IBM PC. This card is based on the NEC D765AC, the large chip at the top of the prototype.

A floppy-disk controller (FDC) is a special-purpose integrated circuit (IC or "flake") and associated deejay controller circuitry that directs and controls reading from and writing to a figurer'southward floppy disk drive (FDD). The FDC is responsible for reading data presented from the host reckoner and converting it to the drive's on-disk format using ane of a number of encoding schemes, like FM encoding (single density) or MFM encoding (double density), and reading those formats and returning it to its original binary values.

Depending on the platform, data transfers betwixt the controller and host computer would be controlled past the figurer's own microprocessor, or an inexpensive dedicated microprocessor like the MOS 6507 or Zilog Z80. Early controllers required additional circuitry to perform specific tasks like providing clock signals and setting various options. Later designs included more of this functionality on the controller and reduced the complication of the external circuitry; single-chip solutions were common past the subsequently 1980s.

Past the 1990s, the floppy deejay was increasingly giving way to hard drives, which required similar controllers. In these systems, the controller also often combined a microcontroller to handle data transfer over standardized connectors like SCSI and IDE that could be used with any computer. In more modern systems, the FDC, if present at all, is typically part of the many functions provided by a single super I/O fleck.

Overview [edit]

A floppy deejay stores binary data not as a series of values, but a series of changes in value. Each of these changes, recorded in the polarity of the magnetic recording media, causes a voltage to be induced in the drive head as the disk surface rotates by it. Information technology is the timing of these polarization changes and the resulting spikes of voltage that encode the ones and zeros of the original data. 1 of the functions of the controller is to plow the original data into the proper pattern of polarizations during writing, and then recreate it during reads.

Equally the storage is based on timing, and that timing is hands affected by mechanical and electric disturbances, accurately reading the information requires some sort of reference indicate, the clock. As the on-disk timing is constantly irresolute, the clock betoken has to be provided past the disk itself. To do this, the original data is modified with extra transitions to allow the clock signal to be encoded in the data and so employ clock recovery during reads to recreate the original signal. Some controllers crave this encoding to be performed externally, but most designs provide standard encodings like FM and MFM.

The controller also provides a number of other services to control the drive mechanism itself. These typically include the movement of the drive caput to eye over the split up tracks on the disk, determining the speed of rotation and attempting to keep it relatively steady, racking the location of the caput and returning information technology to zero, and sometimes functionally to format a disk based on simple inputs like the number of tracks, sectors per track and number of bytes per sector.

To produce a complete arrangement, the controller has to be combined with additional circuitry or software that acts as a bridge betwixt the controller and the host system. In some systems, like the Apple II and IBM PC, this is controlled by software running on the computer'southward host microprocessor and the drive interface is connected directly to the processor using an expansion card. On other systems, similar the Commodore 64 and Atari eight-flake family, there is no direct path from the controller to the host CPU and a second processor like the MOS 6507 or Zilog Z80 is used inside the bulldoze for this purpose.

The original Apple II controller was in the course of a plug-in card on the host calculator. It could support 2 drives, and the drives eliminated well-nigh of the normal onboard circuitry. This allowed Apple to accommodate a deal with Shugart Assembly for a simplified bulldoze that lacked almost of its normal circuitry. This meant that the combined cost of a single drive and controller carte was roughly the same as on other systems, but a 2nd bulldoze could be connected for a smaller additional toll.

The IBM PC took a more conventional approach, their adaptor card could back up upwards to four drives; on the PC direct memory access (DMA) to the drives was performed using IRQ 6. The diagram below shows a conventional floppy deejay controller which communicates with the CPU via an Manufacture Standard Compages (ISA) omnibus or like autobus and communicates with the floppy disk drive with a 34 pin ribbon cable. An alternative organization that is more than usual in contempo designs has the FDC included in a super I/O scrap which communicates via a Low Pin Count (LPC) passenger vehicle.

Block diagram showing FDC communication with the CPU and the FDD.

Most of the floppy disk controller (FDC) functions are performed by the integrated circuit simply some are performed past external hardware circuits. The list of functions performed by each is given below.

Floppy disk controller functions (FDC) [edit]

• Translate data bits into FM, MFM, M²FM, or GCR format to be able to record them
• Interpret and execute commands such as seek, read, write, format, etc.
• Mistake detection with checksums generation and verification, like CRC
• Synchronize data with phase-locked loop (PLL)

External hardware functions [edit]

• Pick of which floppy deejay drive (FDD) to accost
• Switching-on the floppy bulldoze motor
• Reset bespeak for the floppy controller IC
• Enable/disable interrupt and DMA signals in the floppy disk controller (FDC)
• Information separation logic
• Write pre-compensation logic
• Line drivers for signals to the controller
• Line receivers for signals from the controller

Input/output ports for common x86-PC controller [edit]

The FDC has 3 I/O ports. These are:

• Information port
• Main status register (MSR)
• Digital command port

The first two reside inside the FDC IC while the Command port is in the external hardware. The addresses of these three ports are as follows.

Port Address [hex]	Port Name	Location	Port type
3F5	Data port		Bidirectional I/O
3F4	Principal condition register	FDC IC	Input
3F2	Digital command port	External hardware	Output

Data port [edit]

This port is used by the software for three different purposes:

• While issuing a command to the FDC IC, command and command parameter bytes are issued to the FDC IC through this port. The FDC IC stores the different parameters and the command in its internal registers.
• Afterwards a command is executed, the FDC IC stores a set of status parameters in the internal registers. These are read past the CPU through this port. The different status bytes are presented by the FDC IC in a specific sequence.
• In the programmed and interrupt mode of data transfer, the information port is used for transferring data betwixt the FDC IC and the CPU IN or OUT instruction.

Chief condition annals (MSR) [edit]

This port is used by the software to read the overall condition data regarding the FDC IC and the FDD's. Before initiating a floppy disk operation the software reads this port to confirm the readiness status of the FDC and the disk drives to verify the condition of the previously initiated command. The different bits of this register stand for :

Flake	Representation
0	FDD 0: Busy in seek mode
i	FDD ane: Busy in seek mode
2	FDD ii: Busy in seek mode
three	FDD three: Busy in seek way
4	FDC Busy; Read/Write command in progress
five	Non-DMA way
vi	DIO; Indicates the direction of data transfer betwixt the FDC IC and the CPU
7	MQR; Indicates data annals is ready for information transfer

Explanations
MQR	1 = data register ready, 0 = data register not ready
DIO	one = controller has data for CPU, 0 = controller expecting information from CPU
Non-DMA	1 = Controller Non in DMA Fashion, 0 = Controller in DMA Fashion
FDC Decorated	1 = Busy, 0 = Non Busy
FDD 0,ane,2,3	1 = Running, 0 = Not Running

Digital control port [edit]

This port is used by the software to command certain FDD and FDC IC functions. The bit assignments of this port are:

Bit	Representation
0 and i	Device number to be selected
2	RESET FDC IC (Low)
3	Enable FDC interrupt and DMA request signals
4 to vii	Turn ON the motor in disk drive 0, 1, 2 or three respectively

Interface to the floppy disk drive [edit]

The controller connects to the bulldoze using a flat ribbon cable with 34 connectors split between the host, the three.five" drive, and the v.25" drive. This type of cable is called a universal connector.^[1] In the IBM PC family and compatibles, a twist in the cable is used to distinguish disk drives past the socket to which they are connected. All drives are installed with the aforementioned drive select address ready, and the twist in the cable interchange the drive select line at the socket. The drive that is at furthest finish of the cablevision additionally would take a terminating resistor installed to maintain bespeak quality.^[2]

Floppy Drive A Pivot Out

Pin No.	Signal name	Clarification
2	/REDWC	Density Select one=Depression/0=High
4	N/C	Reserved
vi	Due north/C	Reserved
viii	/Alphabetize	0=Index
10	/MOTEA	0=Motor Enable Drive 0
12	/DRVSB	Drive Select 1
fourteen	/DRVSA	Bulldoze Select 0
16	/MOTEB	0=Motor Enable Drive 1
18	/DIR	0=Direction Select
20	/Footstep	0=Head Step
22	/WDATA	Write Data
24	/WGATE	Floppy Write Enable, 0=Write Gate
26	/TRK00	0=Track 00
28	/WPT	0=Write Protect
30	/RDATA	Read Information
32	/SIDE1	1=Side 0/0=Side 1
34	/DSKCHG	one=Disk Change/0=Ready
Odd pins 1 thru 33 are ground

Floppy Drive A/B Twist Pivot Out

	Controller	Drive A	Drive B	Description
Wire one-ix	1-ix	i-nine	1-9	No Change
Wire x	10	16	10	Motor Enable Drive 0/1
Wire eleven	11	15	11	Ground, No Change
Wire 12	12	14	12	Drive Select 0/1
Wire xiii	13	13	thirteen	Footing, No Change
Wire 14	fourteen	12	14	Bulldoze Select 0/1
Wire 15	15	xi	15	Footing, No Change
Wire 16	16	10	16	Motor Enable Bulldoze 0/ane
Wire 17-34	17-34	17-34	17-34	No Modify

More detailed descriptions of the interface signals including culling meanings are contained in manufacturer's specifications for drives.

Format data [edit]

Many mutually incompatible floppy disk formats are possible; bated from the physical format on the deejay, incompatible file systems are also possible.

Drive	Format	Capacity	Transfer speed [kbit/s]	RPM	Tracks	TPI	Comment
8-inch SD	viii-inch SD	fourscore KB	33.333	360	32	48	Only on onetime controllers.[three]
five.25-inch SD	v.25-inch SD	160 KB	125		40		Merely on former controllers.
5.25-inch SSDD	5.25-inch SSDD	171 KB	250–308	300	35	48[4]	Only on C1541 compatibles.
5.25-inch SD	v.25-inch SD	180 KB	150		40		But on onetime controllers.
5.25-inch DD	v.25-inch DD	320/360/400 KB	250	300	xl	48	[five] 8/9/ten 512 byte sectors respectively.
5.25-inch DD (96 tpi)	5.25-inch QD (2DD)	800 KB	250	300	fourscore	96	[6]
5.25-inch HD	5.25-inch DD	360 KB	300	360	xl	48	[7] [8]
5.25" Hard disk	5.25" HD	1200 KB	500	360	fourscore	96	Upwards to 83 tracks. Dissimilar biasing current.[7] [8]
five.25" HD	v.25" HD	720 KB	300	360	80		Up to 83 tracks.[five]
3.5" DD	three.5" DD	720 KB	250	300	80	135	Upwards to 83 tracks.[five] [9]
3.5" DD	three.5" DD	800 KB		394–590	80		Used past Apple Macintosh.[10]
3.five" DD	3.5" DD	800 KB	250	300	80		Used by Commodore 1581.
iii.v" DD	3.v" DD	880 KB	250	300	80		Up to 83 tracks. Used by Amiga computers.
3.5" DD	3.5" DD	360 KB	250	300	forty		[five]
3.5" Hard disk drive	3.5" DD	720 KB	250	300	eighty		Up to 83 tracks.[five]
3.5" Hard disk drive	3.5" Hard disk drive	1440 KB	500	300	lxxx	135	Up to 83 tracks.[5] [11]
iii.5" HD	three.5" HD	1760 KB	250	150	80		Used past Amiga computers.
three.5" ED	3.5" ED	2880 KB	thou	300	80	135	Upwardly to 83 tracks.[nine] [12]

^[13]

Sides:

• SS (or 1S) – Single sided
• DS (or 2S) – Double sided

Density:

• SD (or 1D) – Unmarried density (FM)
• DD (or 2D) – Double density (most often MFM)
• QD (or 4D) – Quad density
• Hd – High density
• ED – Extra-loftier density
• TD – Triple density

"3mode" floppy drive [edit]

A setup disk of Japanese Microsoft Office 4.3, provided with iii.v" ane.ii MB and 1440 KB formats.

Primarily in Japan there are 3.5" high-density floppy drives that back up three modes of disk formats instead of the normal ii – 1440 KB (two MB unformatted), 1.ii MB (i.6 MB unformatted) and 720 KB (1 MB unformatted). Originally, the loftier-density style for 3.5" floppy drives in Nippon only supported a capacity of 1.ii MB instead of the 1440 KB capacity that was used elsewhere.^[14] While the more common 1440 KB format spun at 300 rpm, the 1.2 MB format instead spun at 360 rpm, thereby closely resembling the 1.two MB format with fifteen sectors per track previously found on five.25" high-density floppy drives. After Japanese floppy drives incorporated support for both high-density formats (likewise as the double-density format), hence the name 3mode. Some BIOSes accept a configuration setting to enable this way for floppy drives supporting it.^[15]

Meet also [edit]

• Western Digital FD1771
• Integrated Woz Motorcar (IWM)
• Paula (Amiga controller)
• Floppy disk drive interface
• List of floppy disk formats

References [edit]

1. ^ Davis, Larry (2015-06-13). "Floppy Bulldoze Pinout, Signal names, Pin out Description and Cable twist wiring". www.interfacebus.com . Retrieved 2019-01-29 .
2. ^ Scott Mueller, Upgrading and Repairing PCs, 2nd Edition, Que, 1992, ISBN 0-88022-856-iii,folio 487
3. ^ Ableman, Genna (2005). Elert, Glenn (ed.). "Angular speed of a floppy disk". The Physics Factbook . Retrieved 2022-01-25 .
4. ^ "C 64 Workshop / C= 8 Bit & Peripherals". 1998-05-19. Retrieved 2016-04-18 .
5. ^ ^{a b c d due east f} "unifr.ch – sys/src/kernel/floppy.c". Archived from the original on xix July 2011. Retrieved v May 2011.
6. ^ "Product specification TM100-four flexible disk drive 96, tpi" (PDF) . Retrieved 2022-01-08 .
7. ^ ^{a b} iesleonardo.info – This diskette tutorial provides technical information concerning diskettes
8. ^ ^{a b} oldskool.org – Allow Hard disk 5,25" FDDs operate at 300 rpm instead of 360 rpm
9. ^ ^{a b} intel.com – Intel 82077SL for Super Dumbo Floppies Archived 8 October 2012 at the Wayback Car
10. ^ Johnson, Herbert R. (2016-12-22). "Floppy Bulldoze Tech Info". Retrieved 2017-01-fourteen .
11. ^ yi.org – High Density Floppy Disks Mf2hd Disk 3 v 1 Pk ^{[ permanent dead link ]}
12. ^ mcamafia.de – IBM Personal system/2, three,v"-inch Diskette Drives, Technical Reference
13. ^ "Linux-ii.6.17/drivers/block/floppy.c". ^{[ permanent dead link ]} 090504 gelato.unsw.edu.au
14. ^ books.google.com – Set up Your Own PC by Corey Sandler
15. ^ rojakpot.com – 3mode floppy support

• de Boyne Pollard, Jonathan (2003). "In that location is no such thing as a iii.five-inch floppy disc". Ofttimes Given Answers.
• ISO/IEC 8860-one:1987 Double-Density (DD)
• ISO/IEC 9529-1:1989 High-Density (Hard disk)
• ISO 10994-1:1992 Extra-high-density (ED)
• ECMA-147

Further reading [edit]

• NEC µPD72070 - Floppy Disk Controller Specification Version two.0 (PDF). 2.0 preliminary. NEC Corporation. October 1991. Archived from the original (PDF) on 2017-03-20. Retrieved 2017-03-20 .
• Shah, Katen A. (1996) [September 1992, April 1992]. Intel 82077SL for Super-Dense Floppies (PDF) (Application Notation) (2 ed.). Intel Corporation, IMD Marketing. AP-358, 292093-002. Archived from the original (PDF) on 2017-06-19. Retrieved 2017-06-19 .

External links [edit]

• viralpatel.net A Tutorial on Programming Floppy Deejay Controller
• isdaman.com Programming Floppy Disk Controllers

amatodroseen.blogspot.com

Source: https://en.wikipedia.org/wiki/Floppy-disk_controller

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