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The third, most common version of the 1530 C2N Datassette The Commodore 1530 (C2N) Datasette, later also Datassette (a
portmanteau A portmanteau word, or portmanteau (, ) is a blend of wordsdata In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interpret ...
'' and ''cassette''), is
Commodore Commodore may refer to: Ranks * Commodore (rank), a naval rank ** Commodore (Royal Navy), in the United Kingdom ** Commodore (United States) ** Commodore (Canada) ** Commodore (Finland) ** Commodore (Germany) or ''Kommodore'' * Air commodore ...
's dedicated
magnetic tape data storage Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9- ...
device. Using compact cassettes as the
storage medium Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are conside ...
, it provides inexpensive storage to Commodore's
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses ...
home/personal computers, notably the
PET A pet, or companion animal, is an animal kept primarily for a person's company or entertainment rather than as a working animal, livestock, or a laboratory animal. Popular pets are often considered to have attractive appearances, intelligence ...
,
VIC-20 The VIC-20 (known as the VC-20 in Germany and the VIC-1001 in Japan) 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 ...
, and C64. A physically similar model, Commodore 1531, was made for the Commodore 16 and Plus/4 series computers.


Features

Typical
compact cassette The Compact Cassette or Musicassette (MC), also commonly called the tape cassette, cassette tape, audio cassette, or simply tape or cassette, is an analog magnetic tape recording format for audio recording and playback. Invented by Lou Otte ...
interfaces of the late 1970s use a small controller in the computer to convert digital data to and from analog tones. The interface is then connected to the cassette deck using normal audio cables like
RCA jack The RCA connector is a type of electrical connector commonly used to carry audio and video signals. The name ''RCA'' derives from the company Radio Corporation of America, which introduced the design in the 1930s. The connectors male plug and ...
s or 3.5mm phone jacks. This sort of system was used on the
Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...
and TRS-80 Color Computer, as well as many
S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of p ...
systems, and allow them to be used with any cassette player with suitable connections. left, The Datasette loading process In the Datasette, instead of writing two tones to tape to indicate bits, patterns of
square wave A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum. In an ideal square wave, the transitions b ...
s are used, including a
parity bit A parity bit, or check bit, is a bit added to a string of binary code. Parity bits are a simple form of error detecting code. Parity bits are generally applied to the smallest units of a communication protocol, typically 8-bit octets (bytes), ...
. Programs are written twice to tape for
error correction In information theory and coding theory with applications in computer science and telecommunication, error detection and correction (EDAC) or error control are techniques that enable reliable delivery of digital data over unreliable communi ...
; if an error is detected when reading the first recording, the computer corrects it with data from the second. The Datasette has built-in
analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provide ...
s and
audio filter An audio filter is a frequency dependent circuit, working in the audio frequency range, 0 Hz to 20 kHz. Audio filters can amplify (boost), pass or attenuate (cut) some frequency ranges. Many types of filters exist for different audio a ...
s to convert the computer's
digital data Digital data, in information theory and information systems, is information represented as a string of discrete symbols each of which can take on one of only a finite number of values from some alphabet, such as letters or digits. An exampl ...
into analog audio and vice versa. Connection to the computer is done via a proprietary
edge connector An edge connector is the portion of a printed circuit board (PCB) consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a si ...
(Commodore 1530) or
mini-DIN connector The mini-DIN connectors are a family of multi-pin electrical connectors used in a variety of applications. Mini-DIN is similar to the larger, older DIN connector. Design Mini-DIN connectors are in diameter and come in seven patterns, wit ...
(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, transferring data at around per second. After the Datasette's launch, however, special '' turbo tape'' software appeared, providing much faster tape operation (loading and saving). 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 per side. The use of ''turbo tape'' and other fast loaders increased this number to roughly . The Datasette has only one connection cable, with a –spacing PCB
edge connector An edge connector is the portion of a printed circuit board (PCB) consisting of traces leading to the edge of the board that are intended to plug into a matching socket. The edge connector is a money-saving device because it only requires a si ...
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 In electronics, a pinout (sometimes written "pin-out") is a cross-reference between the contacts, or ''pins'', of an electrical connector or electronic component, and their functions. "Pinout" now supersedes the term "basing diagram" that was the s ...
is ground, , motor, read, write, key-sense. 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 supply via a transistor circuit.


Encoding

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). 091205 wav-prg.sourceforge.net 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 In a computer, an interrupt request (or IRQ) is a hardware signal sent to the processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead. Hardware interrupts are used to handle events s ...
. 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. Inside the tape device the read head signal is fed into an
operational amplifier An operational amplifier (often op amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. In this configuration, an op amp produces an output potential (relative to c ...
(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 Clipping may refer to: Words * Clipping (morphology), the formation of a new word by shortening it, e.g. "ad" from "advertisement" * Clipping (phonetics), shortening the articulation of a speech sound, usually a vowel * Clipping (publications) ...
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 TTL may refer to: Photography * Through-the-lens metering, a camera feature * Zenit TTL, an SLR film camera named for its TTL metering capability Technology * Time to live, a computer data lifespan-limiting mechanism * Transistor–transistor lo ...
electrical level window of the
Schmitt trigger In electronics, a Schmitt trigger is a comparator circuit with hysteresis implemented by applying positive feedback to the noninverting input of a comparator or differential amplifier. It is an active circuit which converts an analog input ...
step that in turn feeds the digital cassette port.Datasette service manual model C2N/1530/1531, preliminary, Oct. 1984 PN-314002-02 On the
PAL Phase Alternating Line (PAL) is a colour encoding system for analogue television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...
version of the C64, the time granularity is (for NTSC ). Since each bit uses this means = or a data rate. Once the bits can be decoded, they are fed into a
shift register A shift register is a type of digital circuit using a cascade of flip-flops where the output of one flip-flop is connected to the input of the next. They share a single clock signal, which causes the data stored in the system to shift from one loc ...
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 ''lead-in byte''. If matched, it's compared to the ''sync byte'' as well. 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.


Models

upThe C2N Cassette Unit, the original Datasette model shape Datassette 1531


PET, VIC-20, C64/128

There are at least four main models of the 1530/C2N Datassette: * The original modified Sanyo M1540A cassette drive, built into the earliest models of PET in 1977. This was a standard shoebox tape recorder with a corner of the case removed and modified electronics; a Commodore PCB was installed internally in place of the Sanyo electronics. To disguise the Sanyo brand, Commodore simply fitted a Commodore badge over the original logo. * The second built-in Datassette in the PET 2001: another standard consumer model (sold in some markets as CCE CCT1020) modified with a Commodore PCB. Black cassette lid, five white keys, no tape counter, no SAVE LED * Black body original-shape model, black cassette lid, five black keys, no tape counter, no SAVE LED * White body original-shape model, black cassette lid, five black keys, with tape counter, no SAVE LED * White body new-shape model, silver cassette lid, six black keys, with white tape counter SAVE LED on left side * White body new-shape model, silver cassette lid, six black keys, with tape counter and a red SAVE LED on the right * As above but with black pattern and silvery Commodore logo, six black keys, tape counter and a red SAVE LED on right side 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 An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematical ...
position. A small
screwdriver A screwdriver is a tool, manual or powered, used for turning screws. A typical simple screwdriver has a handle and a shaft, ending in a tip the user puts into the screw head before turning the handle. This form of the screwdriver has been repla ...
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. Like Datasette models, the recording format is compatible across computers; the VIC, for example, can read PET cassettes.


C16/116 and Plus/4

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 The mini-DIN connectors are a family of multi-pin electrical connectors used in a variety of applications. Mini-DIN is similar to the larger, older DIN connector. Design Mini-DIN connectors are in diameter and come in seven patterns, wit ...
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. *Black/charcoal body new shape model, silver cassette lid, six light gray keys, with tape counter and a red SAVE LED


Popularity

One of the few clones, a Phonemark model 4403 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, while the US magazine ''
Compute!'s Gazette ''Compute!'s Gazette'' (), stylized as ''COMPUTE!'s Gazette'', was a computer magazine of the 1980s, directed at users of Commodore's 8-bit home computers. Announced as ''The Commodore Gazette'', it was a Commodore-only daughter magazine of the ...
'' reported that by 1983 "90 percent of new Commodore 64 owners bought a disk drive with their computer". ''
Computer Gaming World ''Computer Gaming World'' (CGW) was an American computer game magazine published between 1981 and 2006. One of the few magazines of the era to survive the video game crash of 1983, it was sold to Ziff Davis in 1993. It expanded greatly throug ...
'' 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"; by contrast,
MicroProse MicroProse is an American video game publisher and developer founded by Bill Stealey, Sid Meier, and Andy Hollis in 1982. It developed and published numerous games, including starting the ''Civilization'' and '' X-COM'' series. Most of their in ...
reported in 1987 that 80% of its 100,000 sales of ''
Gunship A gunship is a military aircraft armed with heavy aircraft guns, primarily intended for attacking ground targets either as airstrike or as close air support. In modern usage the term "gunship" refers to fixed-wing aircraft having laterally-m ...
'' in the UK were on cassette. 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.


See also

*
Famicom Data Recorder Famicom Data Recorder (HVC-008) is a compact cassette tape data interface introduced in 1984, for the Famicom which had been introduced in 1983. It is compatible with four Famicom games, for saving user-generated content to tapes. As Nintendo's fi ...
*
Fast loader A fast loader is a software program for a home computer, such as the Commodore 64 or ZX Spectrum, that accelerates the speed of file loading from floppy disk or compact cassette. Floppy disks Fast loaders came about because of a discrepa ...
*
IBM cassette tape The original IBM Personal Computer and IBM PCjr included support for storing data and programs on compact cassette tape. It was common for home computers of the time, such as the Apple II, Commodore 64 and BBC Micro, to use cassette tapes for st ...
* Kansas City standard *
Magnetic tape data storage Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9- ...


References


External links


Similar Commodore tape drives



Description of tape format with conversion utilities and code


to build a hardware adaptor/software program to archive Commodore Datasette files to a modern computer.

Digital C2N replacement project.
Sketchup model of the Commodore Datasette 1530.
Sketchup model of the Commodore Datasette 1530. {{Magnetic tape data formats CBM storage devices Home computer peripherals Commodore 64 VIC-20 Tape-based computer storage