The Commodore 1530 (C2N) Datasette, later also Datassette (a portmanteau of data and cassette), is Commodore's dedicated magnetic-tape data storage device. Using compact cassettes as the storage medium, it provides inexpensive storage to Commodore's 8-bit computers, including the PET, VIC-20, and Commodore 64. A physically similar model, Commodore 1531, was made for the Commodore 16 and Plus/4 series computers.
The Datasette is probably the most sophisticated tape-storage method of any microcomputer. [1] Typical compact cassette interfaces of the late 1970s use a small controller in the computer to convert digital data to and from analog audio tones. The interface connects to the cassette deck using normal audio cables like RCA jacks or 3.5mm phone jacks. Such a system is compatible with the Apple II [2] : 57-58 and TRS-80 Color Computer, as well as many S-100 bus systems, and allows them to be used with any cassette player with suitable connections, [3] but using analog tones—similar to how dial-up modems work—often results in read errors instead of successful loading of data. [1]
In the Datasette, instead of writing two tones to tape to indicate bits, patterns of square waves are used, including a parity bit. Programs are written twice to tape for error correction; if an error is detected when reading the first recording, the computer corrects it with data from the second. [1] The Datasette has built-in analog-to-digital converters and audio filters to convert the computer's digital data into analog audio and vice versa. Connection to the computer is done via a proprietary edge connector (Commodore 1530) or mini-DIN connector (1531). The absence of recordable audio signals on this interface makes the Datasette and clones the only cassette recorders usable with Commodore computers, until aftermarket converters made the use of ordinary recorders possible.
Because of its digital format the Datasette is both more reliable than other data cassette systems and very slow, [1] [4] transferring data at around 50 bytes per second. After the Datasette's launch, however, special turbo tape software appeared, providing much faster loading and saving. [1] Such software was integrated into most commercial prerecorded applications (mostly games), as well as being available separately for loading and saving the users' homemade programs and data. These programs were only widely used in Europe, as the US market had long since moved onto disks.
Datasettes can typically store about 100 kByte per 30 minute side. [5] The use of turbo tape and other fast loaders increased this number to roughly 1000 kByte.
The Datasette has only one connection cable, with a 0.156-inch (4.0 mm)–spacing [6] PCB edge connector at the computer end. All input/output signals to the Datasette are all digital, and so all digital-to-analog conversion, and vice versa, is handled within the unit. Power is also included in this cable. The pinout is ground, +5 V DC , motor, read, write, key-sense. [7] The sense signal monitors the play, rewind, and fast-forward buttons but cannot differentiate between them. A mechanical interlock prevents any two of them from being pressed at the same time. The motor power is derived from the computer's unregulated 9 V DC supply [8] via a transistor circuit. [9]
To record physical data, the zero-crossing from positive to negative voltage of the analog signal is measured. The resulting time between these positive to negative crossings is then compared to a threshold to determine whether the time since the last crossing is short (0) or long (1). [10] Note the lower amplitude for the shorter periods.
A circuit in the tape unit transforms the analog signal into a logical 1 or 0, which is then transmitted to the computer via the tape connector. Inside the computer, the first Complex Interface Adapter (6526) in the C64 senses when the signal goes from one to zero. This event is called trigger and causes an interrupt request. This event can be handled by a handler code, or simply discovered by testing bit 4 of location $DC0D. The points that trigger this event are indicated by the black circles in the figure. [10]
Inside the tape device the read head signal is fed into an operational amplifier (1) whose output signal is DC-filtered. Op-amp (2) amplifies and feeds an RC filter. Op-amp (3) amplifies the signal again followed by another DC filter. Op-amp (4) amplifies the signal into clipping the sine-formed signal. The positive and negative rails for all op-amps are wired to +5V DC and GND. The clipped signal therefore fits into the TTL electrical level window of the Schmitt trigger step that in turn feeds the digital cassette port. [11]
On the PAL version of the C64, the time granularity is 1.014 μs (for NTSC 0.978 μs). Since each bit uses 3284 clock cycles this means 3284 * 1.014 μs = 3330 μs/bit. or a 300 bit/s data rate.
Once the bits can be decoded, they are fed into a shift register and are continuously compared to a special bit sequence. This bit sequence can also be seen as a byte. A bit-sequence match means that the stream is byte-synchronized. The first byte to compare with is called the lead-in byte. If matched, it's compared to the sync byte as well. [10]
An example: Turbo Tape 64 has a lead-in byte $02 (binary 00000010), sync byte $09 (binary 00001001) and a following sync sequence of $08, $07, $06, $05, $04, $03, $02, $01. [1] [10]
There are at least four main models of the 1530/C2N Datassette:
The first two external models were made as PET peripherals, and styled after the PET 2001 built-in tape drive. The latter two were styled and marketed for the VIC-20 and C64. All 1530s are compatible with all those computers, as well as the C128.
In addition to this, some models came with a small hole above the keys, to allow access to the adjustment screw of the tape head azimuth position. A small screwdriver can thus easily be used to affect the adjustment without disassembling the Datassette's chassis.
Confusingly, the Datassette at various times was sold both as the C2N DATASETTE UNIT Model 1530 and as the 1530 DATASSETTE UNIT Model C2N. Note the difference in spelling (one S versus two) used on the original product packaging. [14]
Like Datasette models, the recording format is compatible across computers; the VIC, for example, can read PET cassettes. [15] [16]
Similar in physical appearance to the 1530/C2N models is the Commodore 1531, made for the Commodore 16 and Plus/4 series computers. This has a Mini-DIN connector in place of the PCB edge connector. This can be used with a C64/128 via an adaptor, which was supplied by Commodore with some units.
The Datasette was more popular outside than inside the United States. U.S. Gold, which imported American computer games to Britain, often had to wait until they were converted from disk because most British Commodore 64 owners used tape, [17] [18] while the US magazine Compute!'s Gazette reported that by 1983 "90 percent of new Commodore 64 owners bought a disk drive with their computer". [19] Computer Gaming World reported in 1986 that British cassette-based software had failed in the United States because "97% of the Commodore systems in the USA have disk drives"; [20] by contrast, MicroProse reported in 1987 that 80% of its 100,000 sales of Gunship in the UK were on cassette. [21] In the United States disk drives quickly became standard, despite the 1541 costing roughly five times as much as a Datasette. In most parts of Europe, the Datasette was the medium of choice for several years after its launch, although floppy disk drives were generally available. The inexpensive and widely available audio cassettes made the Datasette a good choice for the budget-aware home computer mass market.
The Commodore 1541 is a floppy disk drive which was made by Commodore International for the Commodore 64 (C64), Commodore's most popular home computer. The best-known floppy disk drive for the C64, the 1541 is a single-sided 170-kilobyte drive for 5¼" disks. The 1541 directly followed the Commodore 1540.
The Commodore 64, also known as the C64, is an 8-bit home computer introduced in January 1982 by Commodore International. It has been listed in the Guinness World Records as the highest-selling single computer model of all time, with independent estimates placing the number sold between 12.5 and 17 million units. Volume production started in early 1982, marketing in August for US$595. Preceded by the VIC-20 and Commodore PET, the C64 took its name from its 64 kilobytes(65,536 bytes) of RAM. With support for multicolor sprites and a custom chip for waveform generation, the C64 could create superior visuals and audio compared to systems without such custom hardware.
The MOS Technology 6510 is an 8-bit microprocessor designed by MOS Technology. It is a modified form of the very successful 6502. The 6510 is widely used in the Commodore 64 (C64) home computer and its variants. It is also used in the Seagate ST-251 MFM harddisk.
The VIC-20 is an 8-bit home computer that was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET. The VIC-20 was the first computer of any description to sell one million units, eventually reaching 2.5 million. It was described as "one of the first anti-spectatorial, non-esoteric computers by design...no longer relegated to hobbyist/enthusiasts or those with money, the computer Commodore developed was the computer of the future."
The Commodore PET is a line of personal computers produced starting in 1977 by Commodore International. A single all-in-one case combines a MOS Technology 6502 microprocessor, Commodore BASIC in read-only memory, keyboard, monochrome monitor, and, in early models, a cassette deck.
The Commodore 16 is a home computer made by Commodore International with a 6502-compatible 7501 or 8501 CPU, released in 1984 and intended to be an entry-level computer to replace the VIC-20. A cost-reduced version, the Commodore 116, was mostly sold in Europe.
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Commodore BASIC, also known as PET BASIC or CBM-BASIC, is the dialect of the BASIC programming language used in Commodore International's 8-bit home computer line, stretching from the PET (1977) to the Commodore 128 (1985).
The Commodore 65 is a prototype computer created at Commodore Business Machines in 1990–1991. It is an improved version of the Commodore 64, and it was meant to be backwards-compatible with the older computer, while still providing a number of advanced features close to those of the Amiga.
The Commodore SX-64, also known as the Executive 64, or VIP-64 in Europe, is a portable, briefcase/suitcase-size "luggable" version of the popular Commodore 64 home computer and the first color portable computer.
The KC 85 were models of microcomputers built in East Germany by VEB Mikroelektronik "Wilhelm Pieck" Mühlhausen. The first model in the series, the HC 900, originally designed as a home computer and introduced in 1984, was renamed to KC 85/2 in 1985 to de-emphasize its use as consumer good.
The Commodore 64 home computer used various external peripherals. Due to the backwards compatibility of the Commodore 128, most peripherals would also work on that system. There is also some compatibility with the VIC-20 and Commodore PET.
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The MSD Super Disk were a series of 5¼-inch floppy disk drives compatible to some degree with the Commodore 1541 disk drive. produced by Micro Systems Development for use with Commodore 8-bit home computers. Two different versions of the MSD Super Disk were available: the single-drive model, SD-1; and the dual-drive model, SD-2.
The ZX Spectrum's software library was very diverse. While the majority of the software produced for the system was video games, others included programming language implementations, Sinclair BASIC extensions, databases, word processors, spread sheets, drawing and painting tools, and 3D modelling tools.
The original IBM Personal Computer and IBM PCjr included support for storing data and programs on compact cassette tape.
Commodore 64 disk/tape emulation and data transfer comprises hardware and software for Commodore 64 disk & tape emulation and for data transfer between either Commodore 64 (C64), Commodore (1541) disk drive or Commodore tape deck and newer computers.
The Commodore D9060/D9090 Hard Disks were the only family of hard drives that Commodore made for both the home and business market. The electronics are identical in the D9060 and the larger D9090 unit; the only difference is the size of the installed hard drive, with a jumper set to distinguish between 4 or 6 disk heads. Originally intended for the metal-cased PET/CBM series of computers, they are compatible with the VIC-20, Commodore 64 and later models with an adapter.
The Atari Program Recorder is Atari's dedicated magnetic-tape data storage device for the Atari 8-bit computers. The original 410 was launched along with the Atari 400 and 800 machines in 1979. The 1010 was a smaller model introduced to match the styling of the XL series released in 1983. XC12 of 1986 matched the XE series and was sold mostly in eastern Europe and South America. Slight variations of all of these models were also introduced from time to time.
The Commodore serial bus, is Commodore's interface for primarily magnetic disk data storage and printers for Commodore 8-bit home computers: the VIC-20, Commodore 64, Commodore 128, Plus/4, Commodore 16, and Commodore 65.
