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113-575: The PIC was originally designed as a peripheral for the General Instrument CP1600 , the first commercially available single-chip 16-bit microprocessor . To limit the number of pins required, the CP1600 had a complex highly- multiplexed bus which was difficult to interface with, so in addition to a variety of special-purpose peripherals, General Instrument made the programmable PIC1640 as an all-purpose peripheral. With its own small RAM , ROM and

226-400: A 16-bit processor into a 40-pin dual in-line package (DIP) chip design, the CP1600 multiplexed its data and address pins. This allowed a set of 16 pins to be used for both address selection and reading and writing data, but to do so required two bus cycles. It also complicated the overall machine layout as buffers were required on the memory bus to latch the address while the processor switched

339-434: A PIC on a floppy disk card to read data from a given sector on the disk. The PIC would then read the data into its own internal buffer, watch the bus for unused time when the bus status pins were all zero, and then send data to main memory. General Instrument provided cross-assemblers and simulators/debuggers compatible with 16-bit or larger minicomputers . GI also provided a standalone CP1600 based microcomputer system in

452-443: A button that, when pressed, ejects the disk with varying degrees of force, the discrepancy due to the ejection force provided by the spring of the shutter. In IBM PC compatibles , Commodores, Apple II/IIIs, and other non-Apple-Macintosh machines with standard floppy disk drives, a disk may be ejected manually at any time. The drive has a disk-change switch that detects when a disk is ejected or inserted. Failure of this mechanical switch

565-482: A choice of selectable speeds via software and a 31 kHz low-power source. These devices feature a 14-bit wide code memory, and an improved 8-level deep call stack. The instruction set differs very little from the baseline devices, but the two additional opcode bits allow 128 registers and 2048 words of code to be directly addressed. There are a few additional miscellaneous instructions, and two additional 8-bit literal instructions, add and subtract. The mid-range core

678-632: A customized operating system is used that has no drivers for USB devices. Hardware floppy disk emulators can be made to interface floppy-disk controllers to a USB port that can be used for flash drives. In May 2016, the United States Government Accountability Office released a report that covered the need to upgrade or replace legacy computer systems within federal agencies. According to this document, old IBM Series/1 minicomputers running on 8-inch floppy disks are still used to coordinate "the operational functions of

791-428: A disk can be accessed, the drive needs to synchronize its head position with the disk tracks. In some drives, this is accomplished with a Track Zero Sensor, while for others it involves the drive head striking an immobile reference surface. In either case, the head is moved so that it is approaching track zero position of the disk. When a drive with the sensor has reached track zero, the head stops moving immediately and

904-658: A disk diameter of 8 inches (203.2 mm). Subsequently, the 5¼-inch (133.35 mm) and then the 3½-inch (88.9 mm) became a ubiquitous form of data storage and transfer into the first years of the 21st century. 3½-inch floppy disks can still be used with an external USB floppy disk drive. USB drives for 5¼-inch, 8-inch, and other-size floppy disks are rare to non-existent. Some individuals and organizations continue to use older equipment to read or transfer data from floppy disks. Floppy disks were so common in late 20th-century culture that many electronic and software programs continue to use save icons that look like floppy disks well into

1017-466: A disk, some 3½-inch drives (notably the Macintosh External 400K and 800K drives ) instead use Constant Linear Velocity (CLV), which uses a variable speed drive motor that spins more slowly as the head moves away from the center of the disk, maintaining the same speed of the head(s) relative to the surface(s) of the disk. This allows more sectors to be written to the longer middle and outer tracks as

1130-423: A fabric that removes dust particles from the spinning disk. The three most popular (and commercially available) floppy disks are the 8-inch, 5¼-inch, and 3½-inch floppy disks. Floppy disks store digital data which can be read and written when the disk is inserted into a floppy disk drive ( FDD ) connected to or inside a computer or other device. The first floppy disks, invented and made by IBM in 1971, had

1243-527: A four-level call stack. PIC10F32x devices feature a mid-range 14-bit wide code memory of 256 or 512 words, a 64-byte SRAM register file, and an 8-level deep hardware stack. These devices are available in 6-pin SMD and 8-pin DIP packages (with two pins unused). One input only and three I/O pins are available. A complex set of interrupts are available. Clocks are an internal calibrated high-frequency oscillator of 16 MHz with

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1356-413: A hard-sectored disk, there are many holes, one for each sector row, plus an additional hole in a half-sector position, that is used to indicate sector zero. The Apple II computer system is notable in that it did not have an index hole sensor and ignored the presence of hard or soft sectoring. Instead, it used special repeating data synchronization patterns written to the disk between each sector, to assist

1469-406: A huge variety of PICs are available with various on-board peripherals ( serial communication modules, UARTs , motor control kernels, etc.) and program memory from 256 words to 64K words and more (a "word" is one assembly language instruction, varying in length from 8 to 16 bits , depending on the specific PIC micro family). PIC and PICmicro are now registered trademarks of Microchip Technology. It

1582-507: A keyboard, many tasks would require one or more PICs to build out a complete system. While the design concept had a number of attractive features, General Instrument never strongly marketed the 1600, preferring to deal only with large customers and ignoring the low-end market. This resulted in very little uptake of the system, with the Intellivision being the only really widespread use with about three million units. However, GI had introduced

1695-420: A loaded disk can be removed manually by inserting a straightened paper clip into a small hole at the drive's front panel, just as one would do with a CD-ROM drive in a similar situation. The X68000 has soft-eject 5¼-inch drives. Some late-generation IBM PS/2 machines had soft-eject 3½-inch disk drives as well for which some issues of DOS (i.e. PC DOS 5.02 and higher) offered an EJECT command. Before

1808-590: A parameter of the instruction, while the 9th bit (bit 8) is implicitly specified as 0 by the CALL instruction itself. Lookup tables are implemented using a computed GOTO (assignment to PCL register) into a table of RETLW instructions. RETLW performs a subroutine return and simultaneously loads the W register with an 8-bit immediate constant that is part of the instruction. This "baseline core" does not support interrupts ; all I/O must be polled . There are some "enhanced baseline" variants with interrupt support and

1921-670: A programmable channel controller . At the same time Plessey in the UK released NMOS processors numbered PIC1650 and PIC1655 based on the GI design, using the same instruction sets, either user mask programmable or versions pre-programmed for auto-diallers and keyboard interfaces. In 1998 Microchip introduced the PIC 16F84, a flash programmable and erasable version of its successful serial programmable PIC16C84. In 2001, Microchip introduced more flash programmable devices, with full production commencing in 2002. Today,

2034-557: A recovery. The music and theatre industries still use equipment requiring standard floppy disks (e.g. synthesizers, samplers, drum machines, sequencers, and lighting consoles ). Industrial automation equipment such as programmable machinery and industrial robots may not have a USB interface; data and programs are then loaded from disks, damageable in industrial environments. This equipment may not be replaced due to cost or requirement for continuous availability; existing software emulation and virtualization do not solve this problem because

2147-468: A selectable option and purchasable as an aftermarket OEM add-on. By January 2007, only 2% of computers sold in stores contained built-in floppy disk drives. Floppy disks are used for emergency boots in aging systems lacking support for other bootable media and for BIOS updates, since most BIOS and firmware programs can still be executed from bootable floppy disks . If BIOS updates fail or become corrupt, floppy drives can sometimes be used to perform

2260-457: A series of BEXT instructions pointing at the associated drivers which it runs through one at a time until the device in question sets the EBCI and automatically cause the code to branch. In total, implementing a system using the CP1600 often required additional support chips and logic. This included a system to multiplex sixteen signals into a single pin if the external branching was being used, and

2373-483: A simple CPU for controlling the transfers, it could connect the CP1600 bus to virtually any existing 8-bit peripheral. While this offered considerable power, GI's marketing was limited and the CP1600 was not a success. However, GI had also made the PIC1650, a standalone PIC1640 with additional general-purpose I/O in place of the CP1600 interface. When the company spun off their chip division to form Microchip in 1985, sales of

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2486-505: A single hole in the rotating floppy disk medium line up. This mechanism is used to detect the angular start of each track, and whether or not the disk is rotating at the correct speed. Early 8‑inch and 5¼‑inch disks also had holes for each sector in the enclosed magnetic medium, in addition to the index hole, with the same radial distance from the center, for alignment with the same envelope hole. These were termed hard sectored disks. Later soft- sectored disks have only one index hole in

2599-447: A small circle of floppy magnetic material encased in hard plastic. Earlier types of floppy disks did not have this plastic case, which protects the magnetic material from abuse and damage. A sliding metal cover protects the delicate magnetic surface when the diskette is not in use and automatically opens when the diskette is inserted into the computer. The diskette has a square shape: there are apparently eight possible ways to insert it into

2712-411: A small oblong opening in both sides to allow the drive's heads to read and write data and a large hole in the center to allow the magnetic medium to spin by rotating it from its middle hole. Inside the cover are two layers of fabric with the magnetic medium sandwiched in the middle. The fabric is designed to reduce friction between the medium and the outer cover, and catch particles of debris abraded off

2825-532: A standalone model 1650 PIC in 1976, designed for use without a CP1600. Although not as powerful as the Intel MCS-48 introduced the same year, it was cheaper, and it found a market. Follow-ons included the PIC1670, with instructions widened from 12 to 13 bits to provide twice the address space (64 bytes of RAM and 1024 words of ROM). When GI spun off its chip division to form Microchip Technology in 1985, production of

2938-504: A three-bit-to-eight-line converter to avoid having to decode the bus status signals in external parts. Of the 16-bits available in an instruction opcode , the CP1600 used only 10. The remaining 6 bits were marked "Future Use." The 10-bit instructions meant that code stored in a typical byte-oriented ROM would waste six bits per instruction. In the era of expensive memory, this was a significant issue. To address this, General Instrument also produced special 10-bit ROMs that efficiently stored

3051-546: Is a 16-bit microprocessor created in a partnership between General Instrument and Honeywell , introduced in February 1975. It is one of the first single-chip 16-bit processors. The overall design bears a strong resemblance to the PDP-11 . Honeywell used the CP1600 in a number of process control computers and related systems, but its most widespread use was the CP1610 version in

3164-475: Is a common source of disk corruption if a disk is changed and the drive (and hence the operating system) fails to notice. One of the chief usability problems of the floppy disk is its vulnerability; even inside a closed plastic housing, the disk medium is highly sensitive to dust, condensation and temperature extremes. As with all magnetic storage , it is vulnerable to magnetic fields. Blank disks have been distributed with an extensive set of warnings, cautioning

3277-530: Is a variant of GCC . Instruction ROM is 24 bits wide. Software can access ROM in 16-bit words, where even words hold the least significant 16 bits of each instruction, and odd words hold the most significant 8 bits. The high half of odd words reads as zero. The program counter is 23 bits wide, but the least significant bit is always 0, so there are 22 modifiable bits. Instructions come in two main varieties, with most important operations (add, xor, shifts, etc.) allowing both forms: Microchip's PIC32M products use

3390-551: Is available in the majority of devices labeled PIC12 and PIC16. The first 32 bytes of the register space are allocated to special-purpose registers; the remaining 96 bytes are used for general-purpose RAM. If banked RAM is used, the high 16 registers (0x70–0x7F) are global, as are a few of the most important special-purpose registers, including the STATUS register, which holds the RAM bank select bits. (The other global registers are FSR and INDF,

3503-877: Is being accessed, it is possible to postdecrement, postincrement, or preincrement FSR; or form the effective address by adding W to FSR. In more advanced PIC18 devices, an "extended mode" is available which makes the addressing even more favorable to compiled code: PIC18 devices are still developed (2021) and fitted with CIP (Core Independent Peripherals) In 2001, Microchip introduced the dsPIC series of chips, which entered mass production in late 2004. They are Microchip's first inherently 16-bit microcontrollers. PIC24 devices are designed as general purpose microcontrollers. dsPIC devices include digital signal processing capabilities in addition. Although still similar to earlier PIC architectures, there are significant enhancements: Some features are: dsPICs can be programmed in C using Microchip's XC16 compiler (formerly called C30), which

PIC microcontrollers - Misplaced Pages Continue

3616-451: Is correctly aligned. For a drive without the sensor, the mechanism attempts to move the head the maximum possible number of positions needed to reach track zero, knowing that once this motion is complete, the head will be positioned over track zero. Some drive mechanisms such as the Apple II 5¼-inch drive without a track zero sensor, produce characteristic mechanical noises when trying to move

3729-420: Is generally thought that PIC stands for Peripheral Interface Controller , although General Instruments' original acronym for the initial PIC1640 and PIC1650 devices was " Programmable Interface Controller ". The acronym was quickly replaced with " Programmable Intelligent Computer ". The Microchip 16C84 ( PIC16x84 ), introduced in 1993, was the first Microchip CPU with on-chip EEPROM memory. By 2013, Microchip

3842-417: Is performed, the pins are activated and are used to indicate which of up to sixteen external systems should be sampled. Those devices would then respond to the query by setting EBCI pin, and the state of this pin would then determine whether the branch was taken or not. This could be used, for instance, to test whether an external device had input data that needed to be processed; the processor could express

3955-428: Is still used by software on user-interface elements related to saving files even though physical floppy disks are largely obsolete. Examples of such software include LibreOffice , Microsoft Paint , and WordPad . The 8-inch and 5¼-inch floppy disks contain a magnetically coated round plastic medium with a large circular hole in the center for a drive's spindle. The medium is contained in a square plastic cover that has

4068-445: Is the 1640 "Programmable Interface Controller" , or PIC, which was designed to work in concert with the CP1600 and act as a channel controller for the CPU. As with the other 1640 series chips, the PIC internally decoded the bus logic, but also added a very simple processor that could run its own programs to perform I/O and direct memory access . For instance, one might send an instruction to

4181-449: Is the pic16HV540. "C" devices with quartz windows (for UV erasure) are in general no longer available. These devices feature a 12-bit wide code memory, a 32-byte register file, and a tiny two level deep call stack. They are represented by the PIC10 series, as well as by some PIC12 and PIC16 devices. Baseline devices are available in 6-pin to 40-pin packages. Generally the first 7 to 9 bytes of

4294-500: The Intellivision video game console . The system saw little other use due to General Instrument's marketing philosophy of seeking out customers only with very large orders and ignoring smaller customers. They also did not pursue a second source arrangement, which in the early days of microprocessor designs was a requirement for most potential customers. The CP1600 was implemented in enhancement mode nMOS and required +12, +5, and −3 V power supplies; I/O connections except for

4407-596: The MPLAB and PICKit series. Third party and some open-source tools are also available. Some parts have in-circuit programming capability; low-cost development programmers are available as well as high-volume production programmers. PIC devices are popular with both industrial developers and hobbyists due to their low cost, wide availability, large user base, an extensive collection of application notes, availability of low cost or free development tools, serial programming, and re-programmable flash-memory capability. The original PIC

4520-547: The Type 1 Diskette in 1973, the industry continued to use the terms "floppy disk" or "floppy". In 1976, Shugart Associates introduced the 5¼-inch floppy disk drive. By 1978, there were more than ten manufacturers producing such drives. There were competing floppy disk formats , with hard- and soft-sector versions and encoding schemes such as differential Manchester encoding (DM), modified frequency modulation (MFM), M FM and group coded recording (GCR). The 5¼-inch format displaced

4633-440: The channel controllers seen on mainframe computers . In the floppy controller example, for instance, a single PIC could control the drive, provide a reasonable amount of buffering to improve performance, and then transfer data to and from the host computer using direct memory access (DMA) or through relatively simple code in the CPU. The downside to this approach was cost; while the PIC was not necessary for low-speed devices like

PIC microcontrollers - Misplaced Pages Continue

4746-405: The interrupt handler , which then reads additional data to determine which device called the interrupt. This additional data may be presented using dedicated pins on the CPU, but is often presented as a value on the data bus . The interrupt handler code then decides which device driver to call to process the data. The CP1600 can implement this in fewer instructions; the interrupt handler is simply

4859-507: The video game crash of 1983 led to the closing of the Intellivision production lines in 1984. Production of the CP1600 ended in 1985 when General Instrument spun off its microelectronics division to create Microchip Technology . By this point a number of 32-bit designs like the MC68000 were available that limited interest in a 16-bit design like the CP1600, and their main existing customer,

4972-399: The 1600 could be complex, GI also released the 164x series of support chips with all of the required circuitry built-in. These included keyboard drivers, cassette deck interfaces for storage, and a host of similar systems. For more complex systems, GI introduced the 1640 "Programmable Interface Controller" in 1975. The idea was that a device would use the PIC to handle all the interfacing with

5085-550: The 1618 "Priority Expander". The system included 87 basic instructions. Instructions might be one to three 16-bit words long depending on the addressing format being used. The CP1600 did not support memory-memory indirect addressing (offsets), and looping was implemented using a dedicated adder that performed single-cycle changes to addresses in memory. The arithmetic logic unit (ALU) was 16-bit wide and could add two 16-bit internal registers in 2.4 microseconds, and memory to register adds of 16-bit numbers in 3.2 microseconds. Like

5198-398: The 1990s were non-networked, and floppy disks were the primary means to transfer data between computers, a method known informally as sneakernet . Unlike hard disks, floppy disks were handled and seen; even a novice user could identify a floppy disk. Because of these factors, a picture of a 3½-inch floppy disk became an interface metaphor for saving data. As of 2024 , the floppy disk symbol

5311-469: The 21st century, as a form of skeuomorphic design . While floppy disk drives still have some limited uses, especially with legacy industrial computer equipment , they have been superseded by data storage methods with much greater data storage capacity and data transfer speed , such as USB flash drives , memory cards , optical discs , and storage available through local computer networks and cloud storage . The first commercial floppy disks, developed in

5424-518: The 720 KB double density 3½-inch microfloppy disk on its Convertible laptop computer in 1986 and the 1.44 MB (1,474,560 bytes) high-density version with the IBM Personal System/2 (PS/2) line in 1987. These disk drives could be added to older PC models. In 1988, Y-E Data introduced a drive for 2.88 MB Double-Sided Extended-Density (DSED) diskettes which was used by IBM in its top-of-the-line PS/2 and some RS/6000 models and in

5537-530: The 8-inch one for most uses, and the hard-sectored disk format disappeared. The most common capacity of the 5¼-inch format in DOS-based PCs was 360 KB (368,640 bytes) for the Double-Sided Double-Density (DSDD) format using MFM encoding. In 1984, IBM introduced with its PC/AT the 1.2 MB (1,228,800 bytes) dual-sided 5¼-inch floppy disk, but it never became very popular. IBM started using

5650-517: The BSR ( a =1). A 1-level stack is also available for the STATUS, WREG and BSR registers. They are saved on every interrupt, and may be restored on return. If interrupts are disabled, they may also be used on subroutine call/return by setting the s bit (appending ", FAST" to the instruction). The auto increment/decrement feature was improved by removing the control bits and adding four new indirect registers per FSR. Depending on which indirect file register

5763-432: The CP1600 ended. By this time, however, the PIC 1650 had developed a large market of customers using it for a wide variety of roles, and the PIC went on to become one of the new company's primary products. In 1985, General Instrument sold their microelectronics division and the new owners cancelled almost everything which by this time was mostly out-of-date. The PIC, however, was upgraded with an internal EPROM to produce

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5876-455: The CP1600 were all but dead, but the PIC1650 and successors had formed a major market of their own, and they became one of the new company's primary products. Early models only had mask ROM for code storage, but with its spinoff it was soon upgraded to use EPROM and then EEPROM , which made it possible for end-users to program the devices in their own facilities. All current models use flash memory for program storage, and newer models allow

5989-474: The CPU as it changed the bus from indicating an address to data. This both negatively affected I/O performance and increased the complexity of the I/O devices. To address this problem, GI supplied a series of 164x dedicated I/O chips that implemented the required bus logic. These included, for instance, the 1641 keyboard controller, the 1643 cassette tape controller, and the 1647 display control. Most famous among these

6102-643: The GIC1600. The CP1610, used in game consoles such as the Champion 2711 and most notably the Intellivision , is a compatible member of the 1600 microprocessor family. It uses a 2 MHz two-phase clock producing a 1 microsecond processor cycle. The CP1610 in the NTSC Intellivisions uses a 1.7897725 MHz two-phase clock. Although users of the CP1600 in the traditional computer role were relatively rare, over 3 million Intellivisions were produced from 1980 until

6215-436: The Intellivision, was no longer in production. Many other products were also end-of-lifed at the same time, and their primary product was the PIC. Floppy disk drive A floppy disk or floppy diskette (casually referred to as a floppy , a diskette , or a disk ) is a type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined with

6328-513: The PDP-11, the CP1600 used eight 16-bit "general purpose" processor registers , although they were not truly general-purpose as in modern designs. Only R0 had no pre-defined purpose and has been described as "the primary accumulator". R1 through R3 could be used data pointers, generally used for register-based addressing ("implied addressing"). R4 and R5 auto-incremented after being accessed, which made them useful for looping over collections of data. R6

6441-914: The PIC to reprogram itself. Since then the line has seen significant change; memory is now available in 8-bit, 16-bit, and, in latest models, 32-bit wide. Program instructions vary in bit-count by family of PIC, and may be 12, 14, 16, or 24 bits long. The instruction set also varies by model, with more powerful chips adding instructions for digital signal processing functions. The hardware implementations of PIC devices range from 6-pin SMD , 8-pin DIP chips up to 144-pin SMD chips, with discrete I/O pins, ADC and DAC modules, and communications ports such as UART , I2C , CAN , and even USB . Low-power and high-speed variations exist for many types. The manufacturer supplies computer software for development known as MPLAB X , assemblers and C/C++ compilers, and programmer/debugger hardware under

6554-655: The PIC trademark, but have a completely different architecture, and are described here only briefly. In November 2007, Microchip introduced the PIC32MX family of 32-bit microcontrollers, based on the MIPS32 M4K Core . The device can be programmed using the Microchip MPLAB C Compiler for PIC32 MCUs , a variant of the GCC compiler. The first 18 models currently in production (PIC32MX3xx and PIC32MX4xx) are pin to pin compatible and share

6667-473: The PIC18 architecture (however, see clones below). The PIC17 series is not recommended for new designs, and availability may be limited to users. Improvements over earlier cores are 16-bit wide opcodes (allowing many new instructions), and a 16-level deep call stack. PIC17 devices were produced in packages from 40 to 68 pins. The PIC17 series introduced a number of important new features: A significant limitation

6780-613: The PIC32MZ series of microcontrollers, based on the MIPS M14K core. The PIC32MZ series include: In 2015, Microchip released the PIC32MZ EF family, using the updated MIPS M5150 Warrior M-class processor. In 2017, Microchip introduced the PIC32MZ DA Family, featuring an integrated graphics controller, graphics processor and 32MB of DDR2 DRAM. General Instrument CP1600 The CP1600

6893-469: The Sony design, introduced in 1983 by many manufacturers, was then rapidly adopted. By 1988, the 3½-inch was outselling the 5¼-inch. Generally, the term floppy disk persisted, even though later style floppy disks have a rigid case around an internal floppy disk. By the end of the 1980s, 5¼-inch disks had been superseded by 3½-inch disks. During this time, PCs frequently came equipped with drives of both sizes. By

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7006-636: The United States' nuclear forces". The government planned to update some of the technology by the end of the 2017 fiscal year. Use in Japan's government ended in 2024. Windows 10 and Windows 11 no longer come with drivers for floppy disk drives (both internal and external). However, they will still support them with a separate device driver provided by Microsoft. The British Airways Boeing 747-400 fleet, up to its retirement in 2020, used 3½-inch floppy disks to load avionics software. Sony, who had been in

7119-411: The bank select bits. Because of the very limited register space (5 bits), 4 rarely read registers were not assigned addresses, but written by special instructions ( OPTION and TRIS ). The ROM address space is 512 and may only specify addresses in the first half of each 512-word page. That is, the CALL instruction specifies the low 9 bits of the address, but only the low 8 bits of that address are

7232-463: The clocks were TTL (5 V) compatible. Each microstate or processor cycle uses four internal time slots generated by two non-overlapping clocks. A 3.3 MHz two-phase clock produces a 600 nanosecond microcycle. A 5 MHz two-phase clock produces a 400 nanosecond microcycle. Due to the voltage requirements of the clock signals, these had to be generated with external circuitry, as was common in this era of microprocessor design. In order to fit

7345-409: The computer in finding and synchronizing with the data in each track. The later 3½-inch drives of the mid-1980s did not use sector index holes, but instead also used synchronization patterns. Most 3½-inch drives used a constant speed drive motor and contain the same number of sectors across all tracks. This is sometimes referred to as Constant Angular Velocity (CAV). In order to fit more data onto

7458-406: The corresponding sensor; this was mainly a hardware cost-saving measure. The core of the 3½-inch disk is the same as the other two disks, but the front has only a label and a small opening for reading and writing data, protected by the shutter—a spring-loaded metal or plastic cover, pushed to the side on entry into the drive. Rather than having a hole in the center, it has a metal hub which mates to

7571-399: The current is reversed the magnetization aligns in the opposite direction, encoding one bit of data. To read data, the magnetization of the particles in the media induce a tiny voltage in the head coil as they pass under it. This small signal is amplified and sent to the floppy disk controller , which converts the streams of pulses from the media into data, checks it for errors, and sends it to

7684-399: The disk media, an action originally accomplished by a disk-load solenoid. Later drives held the heads out of contact until a front-panel lever was rotated (5¼-inch) or disk insertion was complete (3½-inch). To write data, current is sent through a coil in the head as the media rotates. The head's magnetic field aligns the magnetization of the particles directly below the head on the media. When

7797-442: The disk shell are not quite square: its width is slightly less than its depth, so that it is impossible to insert the disk into a drive slot sideways (i.e. rotated 90 degrees from the correct shutter-first orientation). A diagonal notch at top right ensures that the disk is inserted into the drive in the correct orientation—not upside down or label-end first—and an arrow at top left indicates direction of insertion. The drive usually has

7910-466: The disk to keep them from accumulating on the heads. The cover is usually a one-part sheet, double-folded with flaps glued or spot-welded together. A small notch on the side of the disk identifies whether it is writable, as detected by a mechanical switch or photoelectric sensor . In the 8-inch disk, the notch being covered or not present enables writing, while in the 5¼-inch disk, the notch being present and uncovered enables writing. Tape may be used over

8023-406: The eight ways one might try to insert the diskette, only one is correct, and only that one will fit. An excellent design. A spindle motor in the drive rotates the magnetic medium at a certain speed, while a stepper motor-operated mechanism moves the magnetic read/write heads radially along the surface of the disk. Both read and write operations require the media to be rotating and the head to contact

8136-687: The existing 3½-inch designs was the SuperDisk in the late 1990s, using very narrow data tracks and a high precision head guidance mechanism with a capacity of 120 MB and backward-compatibility with standard 3½-inch floppies; a format war briefly occurred between SuperDisk and other high-density floppy-disk products, although ultimately recordable CDs/DVDs, solid-state flash storage, and eventually cloud-based online storage would render all these removable disk formats obsolete. External USB -based floppy disk drives are still available, and many modern systems provide firmware support for booting from such drives. In

8249-555: The flexibility of floppy disks combined with greater capacity, but remained niche due to costs. High-capacity backward compatible floppy technologies became popular for a while and were sold as an option or even included in standard PCs, but in the long run, their use was limited to professionals and enthusiasts. Flash-based USB thumb drives finally were a practical and popular replacement, that supported traditional file systems and all common usage scenarios of floppy disks. As opposed to other solutions, no new drive type or special software

8362-457: The floppy disk business since 1983, ended domestic sales of all six 3½-inch floppy disk models as of March 2011. This has been viewed by some as the end of the floppy disk. While production of new floppy disk media has ceased, sales and uses of this media from inventories is expected to continue until at least 2026. For more than two decades, the floppy disk was the primary external writable storage device used. Most computing environments before

8475-512: The general population, floppy disks were often used to store a computer's operating system (OS). Most home computers from that time have an elementary OS and BASIC stored in read-only memory (ROM), with the option of loading a more advanced OS from a floppy disk. By the early 1990s, the increasing software size meant large packages like Windows or Adobe Photoshop required a dozen disks or more. In 1996, there were an estimated five billion standard floppy disks in use. An attempt to enhance

8588-431: The greater capacity, compatibility with existing CD-ROM drives, and—with the advent of re-writeable CDs and packet writing—a similar reusability as floppy disks. However, CD-R/RWs remained mostly an archival medium, not a medium for exchanging data or editing files on the medium itself, because there was no common standard for packet writing which allowed for small updates. Other formats, such as magneto-optical discs , had

8701-407: The heads past the reference surface. This physical striking is responsible for the 5¼-inch drive clicking during the boot of an Apple II, and the loud rattles of its DOS and ProDOS when disk errors occurred and track zero synchronization was attempted. All 8-inch and some 5¼-inch drives used a mechanical method to locate sectors, known as either hard sectors or soft sectors , and is the purpose of

8814-450: The host computer system. A blank unformatted diskette has a coating of magnetic oxide with no magnetic order to the particles. During formatting, the magnetizations of the particles are aligned forming tracks, each broken up into sectors , enabling the controller to properly read and write data. The tracks are concentric rings around the center, with spaces between tracks where no data is written; gaps with padding bytes are provided between

8927-426: The host computer's CP1600, but also use its own internal processor to handle the actual device it was connected to. For instance, a floppy disk drive could be implemented with a PIC talking to the CPU on one side and the floppy disk controller on the other. In keeping with this idea, what would today be known as a microcontroller , the PIC included a small amount of read-only memory (ROM) that would be written with

9040-476: The instructions. As data and addresses would still require 16-bit values, the 1600 included a special SDBD instruction that pieced together a 16-bit argument from two 10-bit ROM reads. The unused 6 bits were intended to be used with co-processors, asserting the PCIT line which stalled the CPU until released. Early documentation shows two planned chips in the series, the 1616 which added the "Extended Instruction Set", and

9153-499: The late 1960s, were 8 inches (203.2 mm) in diameter; they became commercially available in 1971 as a component of IBM products and both drives and disks were then sold separately starting in 1972 by Memorex and others. These disks and associated drives were produced and improved upon by IBM and other companies such as Memorex, Shugart Associates , and Burroughs Corporation . The term "floppy disk" appeared in print as early as 1970, and although IBM announced its first media as

9266-530: The low 8 bits of the program counter PCL, the PC high preload register PCLATH, and the master interrupt control register INTCON.) The PCLATH register supplies high-order instruction address bits when the 8 bits supplied by a write to the PCL register, or the 11 bits supplied by a GOTO or CALL instruction, are not sufficient to address the available ROM space. The PIC17 series never became popular and has been superseded by

9379-486: The machine instructions vary by family and are shown in PIC instruction listings . Within these families, devices may be designated PICnnCxxx (CMOS) or PICnnFxxx (Flash). "C" devices are generally classified as "Not suitable for new development" (not actively promoted by Microchip). The program memory of "C" devices is variously described as OTP, ROM, or EEPROM. As of October 2016, the only OTP product classified as "In production"

9492-424: The machine, only one of which is correct. What happens if I do it wrong? I try inserting the disk sideways. Ah, the designer thought of that. A little study shows that the case really isn't square: it's rectangular, so you can't insert a longer side. I try backward. The diskette goes in only part of the way. Small protrusions, indentations, and cutouts prevent the diskette from being inserted backward or upside down: of

9605-399: The media. In some 5¼-inch drives, insertion of the disk compresses and locks an ejection spring which partially ejects the disk upon opening the catch or lever. This enables a smaller concave area for the thumb and fingers to grasp the disk during removal. Newer 5¼-inch drives and all 3½-inch drives automatically engage the spindle and heads when a disk is inserted, doing the opposite with

9718-400: The medium, and sector position is determined by the disk controller or low-level software from patterns marking the start of a sector. Generally, the same drives are used to read and write both types of disks, with only the disks and controllers differing. Some operating systems using soft sectors, such as Apple DOS , do not use the index hole, and the drives designed for such systems often lack

9831-493: The mid-1990s, 5¼-inch drives had virtually disappeared, as the 3½-inch disk became the predominant floppy disk. The advantages of the 3½-inch disk were its higher capacity, its smaller physical size, and its rigid case which provided better protection from dirt and other environmental risks. Floppy disks became commonplace during the 1980s and 1990s in their use with personal computers to distribute software, transfer data, and create backups . Before hard disks became affordable to

9944-479: The mid-1990s, mechanically incompatible higher-density floppy disks were introduced, like the Iomega Zip disk . Adoption was limited by the competition between proprietary formats and the need to buy expensive drives for computers where the disks would be used. In some cases, failure in market penetration was exacerbated by the release of higher-capacity versions of the drive and media being not backward-compatible with

10057-526: The notch to change the mode of the disk. Punch devices were sold to convert read-only 5¼" disks to writable ones, and also to enable writing on the unused side of single-sided disks for computers with single-sided drives. The latter worked because single- and double-sided disks typically contained essentially identical actual magnetic media, for manufacturing efficiency. Disks whose obverse and reverse sides were thus used separately in single-sided drives were known as flippy disks . Disk notching 5¼" floppies for PCs

10170-485: The old format, including a rigid case with a sliding metal (or later, sometimes plastic) shutter over the head slot, which helped protect the delicate magnetic medium from dust and damage, and a sliding write protection tab, which was far more convenient than the adhesive tabs used with earlier disks. The large market share of the well-established 5¼-inch format made it difficult for these diverse mutually-incompatible new formats to gain significant market share. A variant on

10283-492: The original drives, dividing the users between new and old adopters. Consumers were wary of making costly investments into unproven and rapidly changing technologies, so none of the technologies became the established standard. Apple introduced the iMac G3 in 1998 with a CD-ROM drive but no floppy drive; this made USB-connected floppy drives popular accessories, as the iMac came without any writable removable media device. Recordable CDs were touted as an alternative, because of

10396-488: The pins to data mode. The interface to the system was likewise complex, requiring three pins, BDIR , BC1 and BC2 , which had to be decoded to understand what state the memory bus was in. A relatively uncommon feature of the CP1600 was its "external branch" concept. This was implemented as four pins on the chip, EBCA0 through EBCA3 , which held the lower four bits of the BEXT instruction opcode. When this instruction

10509-450: The predominant development language. The PIC18 series inherits most of the features and instructions of the PIC17 series, while adding a number of important new features: The RAM space is 12 bits, addressed using a 4-bit bank select register (BSR) and an 8-bit offset in each instruction. An additional "access" bit in each instruction selects between bank 0 ( a =0) and the bank selected by

10622-409: The press of the eject button. On Apple Macintosh computers with built-in 3½-inch disk drives, the ejection button is replaced by software controlling an ejection motor which only does so when the operating system no longer needs to access the drive. The user could drag the image of the floppy drive to the trash can on the desktop to eject the disk. In the case of a power failure or drive malfunction,

10735-403: The read operation; other errors are permanent and the disk controller will signal a failure to the operating system if multiple attempts to read the data still fail. After a disk is inserted, a catch or lever at the front of the drive is manually lowered to prevent the disk from accidentally emerging, engage the spindle clamping hub, and in two-sided drives, engage the second read/write head with

10848-548: The register file are special-purpose registers, and the remaining bytes are general purpose RAM. Pointers are implemented using a register pair: after writing an address to the FSR (file select register), the INDF (indirect f) register becomes an alias for the addressed register. If banked RAM is implemented, the bank number is selected by the high 3 bits of the FSR. This affects register numbers 16–31; registers 0–15 are global and not affected by

10961-513: The same peripherals set with the PIC24FxxGA0xx family of (16-bit) devices, allowing the use of common libraries, software and hardware tools. Today, starting at 28 pin in small QFN packages up to high performance devices with Ethernet, CAN and USB OTG, full family range of mid-range 32-bit microcontrollers are available. The PIC32 architecture brought a number of new features to Microchip portfolio, including: In November 2013, Microchip introduced

11074-651: The second-generation NeXTcube and NeXTstation ; however, this format had limited market success due to lack of standards and movement to 1.44 MB drives. Throughout the early 1980s, limits of the 5¼-inch format became clear. Originally designed to be more practical than the 8-inch format, it was becoming considered too large; as the quality of recording media grew, data could be stored in a smaller area. Several solutions were developed, with drives at 2-, 2½-, 3-, 3¼-, 3½- and 4-inches (and Sony 's 90 mm × 94 mm (3.54 in × 3.70 in) disk) offered by various companies. They all had several advantages over

11187-502: The sectors and at the end of the track to allow for slight speed variations in the disk drive, and to permit better interoperability with disk drives connected to other similar systems. Each sector of data has a header that identifies the sector location on the disk. A cyclic redundancy check (CRC) is written into the sector headers and at the end of the user data so that the disk controller can detect potential errors. Some errors are soft and can be resolved by automatically re-trying

11300-413: The small hole in the jacket, off to the side of the spindle hole. A light beam sensor detects when a punched hole in the disk is visible through the hole in the jacket. For a soft-sectored disk, there is only a single hole, which is used to locate the first sector of each track. Clock timing is then used to find the other sectors behind it, which requires precise speed regulation of the drive motor. For

11413-408: The spindle of the drive. Typical 3½-inch disk magnetic coating materials are: Two holes at the bottom left and right indicate whether the disk is write-protected and whether it is high-density; these holes are spaced as far apart as the holes in punched A4 paper, allowing write-protected high-density floppy disks to be clipped into international standard ( ISO 838 ) ring binders . The dimensions of

11526-442: The user not to expose it to dangerous conditions. Rough treatment or removing the disk from the drive while the magnetic media is still spinning is likely to cause damage to the disk, drive head, or stored data. On the other hand, the 3½‑inch floppy disk has been lauded for its mechanical usability by human–computer interaction expert Donald Norman : A simple example of a good design is the 3½-inch magnetic diskette for computers,

11639-437: The user's device controller code, and a separate random access memory (RAM) for buffering and working with data. These were connected separately, making the PIC a Harvard architecture system with code and data being managed on separate internal pathways. In theory, the combination of 1600 CPU and 1640 PIC device controllers provided a very high-performance device control system, one that was similar in power and performance to

11752-447: The value "2" on the EBCA to sample device 2, call the BEXT , and that device would then respond by setting EBCI to true if there was data, causing the processor to jump into the code to read the data from that device. This contrasts with the typical solution for handling external devices; most systems have the devices raise an interrupt which causes the processor to call special code,

11865-418: Was being presented at a time, the devices had to watch the bus to go into address mode, see if that address was part of its memory mapped input/output range, "latch" that address and then wait for the data mode to turn on and then read the value. Additionally, the 1600 used several external pins to select which device it was attempting to talk to, further complicating the interfacing. As interfacing devices to

11978-409: Was generally only required where users wanted to overwrite original 5¼" disks of store-bought software, which somewhat commonly shipped with no notch present. Another LED/photo-transistor pair located near the center of the disk detects the index hole once per rotation in the magnetic disk. Detection occurs whenever the drive's sensor, the holes in the correctly inserted floppy's plastic envelope and

12091-445: Was intended to be used with General Instrument's new CP1600 16-bit central processing unit (CPU). In order to fit 16-bit data and address buses into a then-standard 40-pin dual inline package (DIP) chip, the two buses shared the same set of 16 connection pins. In order to communicate with the CPU, devices had to watch other pins on the CPU to determine if the information on the bus was an address or data. Since only one of these

12204-468: Was little financial incentive to omit the device from a system. Subsequently, enabled by the widespread support for USB flash drives and BIOS boot, manufacturers and retailers progressively reduced the availability of floppy disk drives as standard equipment. In February 2003, Dell , one of the leading personal computer vendors, announced that floppy drives would no longer be pre-installed on Dell Dimension home computers, although they were still available as

12317-443: Was required that impeded adoption, since all that was necessary was an already common USB port . By 2002, most manufacturers still provided floppy disk drives as standard equipment to meet user demand for file-transfer and an emergency boot device, as well as for the general secure feeling of having the familiar device. By this time, the retail cost of a floppy drive had fallen to around $ 20 (equivalent to $ 34 in 2023), so there

12430-489: Was shipping over one billion PIC microcontrollers every year. PIC micro chips are designed with a Harvard architecture , and are offered in various device families. The baseline and mid-range families use 8-bit wide data memory, and the high-end families use 16-bit data memory. The latest series, PIC32MZ, is a 32-bit MIPS -based microcontroller. Instruction word sizes are 12 bits (PIC10 and PIC12), 14 bits (PIC16) and 24 bits (PIC24 and dsPIC). The binary representations of

12543-479: Was that RAM space was limited to 256 bytes (26 bytes of special function registers, and 232 bytes of general-purpose RAM), with awkward bank-switching in the models that supported more. In 2000, Microchip introduced the PIC18 architecture. Unlike the PIC17 series, it has proven to be very popular, with a large number of device variants presently in manufacture. In contrast to earlier devices, which were more often than not programmed in assembly language , C has become

12656-402: Was the stack pointer , R7 the program counter. Since both of these registers were visible to the programmer, they could be used to implement multiple stacks, or support more complex branching, among other things. There were no implicit stack instructions; when R6 was used in a "read" operation it decremented the address and then returned the data being pointed at, simulating a POP , and when it

12769-512: Was used in a "write" it would write then post-increment (like R4/R5), simulating a PUSH . As was common for the era, the CP1600 used memory-mapped I/O , as opposed to separate I/O pins as seen on the Intel systems. The use of a multiplexed bus and multi-state bus status made implementing I/O more difficult than would normally be the case on memory-mapped systems. This meant that implementations had to use latches or buffers to be able to interface with

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