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Commodore Datasette

December 15, 2023

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 third, most common version of the 1530 C2N Datassette

Features edit

 
The connection cable to the Datasette

Typical compact cassette 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 jacks or 3.5mm phone jacks. This sort of system was used on the Apple II[1]: 57-58  and TRS-80 Color Computer, as well as many S-100 bus systems, and allow them to be used with any cassette player with suitable connections.[2]

 
The Datasette loading process

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.[3] 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,[3][4] transferring data at around 50 bytes 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 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]

Encoding edit

 
Inside the Datasette
 
The resulting waveform from storing data
 
Datasette sound sample
Commodore Datasette 18-second sound sample
Problems playing this file? See media help.

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 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.[3][10]

Models edit

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

PET, VIC-20, C64/128 edit

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.[12]
  • 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[13]
  • 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 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]

C16/116 and Plus/4 edit

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.

  • Black/charcoal body new shape model, silver cassette lid, six light gray keys, with tape counter and a red SAVE LED

Popularity edit

 
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,[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.

See also edit

References edit

  1. ^ "The Apple II Cassette Interface". Apple Orchard. Vol. 2, no. 1. International Apple Core. Spring 1981. p. 57-58. ISSN 0277-1950. OCLC 647837472 – via Internet Archive.
  2. ^ Friedman, Herb (February 1983). "The Five Friendliest Computers". Popular Mechanics. p. 97.
  3. ^ a b c De Ceukelaire, Harrie (February 1985). "How TurboTape Works". Compute!. p. 112. Retrieved 30 October 2013.
  4. ^ Waite, Mitchell; Lafore, Robert; Volpe, Jerry (1985). "Peripherals: Displays, Disk Drives, Printers, and More". The Official Book for the Commodore 128 Personal Computer. Howard W. Sams & Co. pp. 11–32. ISBN 0-672-22456-9.
  5. ^ "Basic Commodore information".[permanent dead link]
  6. ^ Rupert, Dale (July 1987). "Rupert Report: Computers in Control". Ahoy!. New York: Ion International. p. 32. ISSN 8750-4383. Retrieved 2018-04-12.
  7. ^ pinouts.ru - C64 Cassette pinout, 2012-01-15
  8. ^ Commodore 64 Programmer's Reference Guide. West Chester: Commodore Business Machines. 1984. Commodore 64 Schematic Diagram. ISBN 0-672-22056-3. Retrieved 2018-04-12.
  9. ^ SAMS Computerfacts CC4: Computer: Commodore 64. Indianapolis: Howard W. Sams. 1984. p. 2.
  10. ^ a b c d "How Commodore tapes work". 091205 wav-prg.sourceforge.net
  11. ^ Datasette service manual model C2N/1530/1531, preliminary, Oct. 1984 PN-314002-02
  12. ^ http://www.zimmers.net/anonftp/pub/cbm/faq/trivia/cbm-trivia-13.txt[bare URL plain text file]
  13. ^ Abril, Editora (26 October 1973). "Placar Magazine". Editora Abril. Retrieved 27 June 2017 – via Google Books.
  14. ^ Bo Zimmerman. "Commodore Datasettes". Commodore Gallery. Retrieved 20 April 2012.
  15. ^ Thornburg, David D. (April 1981). "The Commodore VIC-20: A First Look". Compute!. p. 26.
  16. ^ Butterfield, JIm (April 1981). "Advice to PET Owners: How To Be A VIC Expert". Compute!. No. 11. p. 34.
  17. ^ Anderson, Chris (June 1985). "On top of the US Goldmine". Zzap!64 (interview). pp. 46–48. Retrieved 26 October 2013.
  18. ^ Pountain, Dick (January 1985). "The Amstrad CPC 464". BYTE. pp. 401. Retrieved 27 October 2013.
  19. ^ Halfhill, Tom (Dec 1983). "The Editor's Notes". Compute!'s Gazette (editorial). p. 6. Retrieved 6 February 2016.
  20. ^ Wagner, Roy (August 1986). "The Commodore Key". Computer Gaming World. p. 28. Retrieved 1 November 2013.
  21. ^ Brooks, M. Evan (November 1987). "Titans of the Computer Gaming World / MicroProse". Computer Gaming World. p. 16. Retrieved 2 November 2013.

External links edit

  • Datasette photos
  • Description of tape format with conversion utilities and code
  • C2N232 project to build a hardware adaptor/software program to archive Commodore Datasette files to a modern computer.
  • DC2N Homepage Digital C2N replacement project.
  • Sketchup model of the Commodore Datasette 1530. Sketchup model of the Commodore Datasette 1530.

December 15, 2023
commodore, datasette, commodore, 1530, datasette, later, also, datassette, portmanteau, data, cassette, commodore, dedicated, magnetic, tape, data, storage, device, using, compact, cassettes, storage, medium, provides, inexpensive, storage, commodore, computer. 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 third most common version of the 1530 C2N Datassette Contents 1 Features 2 Encoding 3 Models 3 1 PET VIC 20 C64 128 3 2 C16 116 and Plus 4 4 Popularity 5 See also 6 References 7 External linksFeatures edit nbsp The connection cable to the DatasetteTypical compact cassette 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 jacks or 3 5mm phone jacks This sort of system was used on the Apple II 1 57 58 and TRS 80 Color Computer as well as many S 100 bus systems and allow them to be used with any cassette player with suitable connections 2 nbsp The Datasette loading processIn 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 3 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 3 4 transferring data at around 50 bytes 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 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 Encoding edit nbsp Inside the Datasette nbsp The resulting waveform from storing data nbsp Datasette sound sample source source Commodore Datasette 18 second sound sample Problems playing this file See media help 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 ms for NTSC 0 978 ms Since each bit uses 3284 clock cycles this means 3284 1 014 ms 3330 ms 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 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 3 10 Models edit nbsp The C2N Cassette Unit the original Datasette model shape nbsp Datassette 1531PET VIC 20 C64 128 edit 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 12 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 13 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 sideThe 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 C16 116 and Plus 4 edit 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 Black charcoal body new shape model silver cassette lid six light gray keys with tape counter and a red SAVE LEDPopularity edit nbsp One of the few clones a Phonemark model 4403The 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 See also editFamicom Data Recorder Fast loader IBM cassette tape Kansas City standard Magnetic tape data storageReferences edit The Apple II Cassette Interface Apple Orchard Vol 2 no 1 International Apple Core Spring 1981 p 57 58 ISSN 0277 1950 OCLC 647837472 via Internet Archive Friedman Herb February 1983 The Five Friendliest Computers Popular Mechanics p 97 a b c De Ceukelaire Harrie February 1985 How TurboTape Works Compute p 112 Retrieved 30 October 2013 Waite Mitchell Lafore Robert Volpe Jerry 1985 Peripherals Displays Disk Drives Printers and More The Official Book for the Commodore 128 Personal Computer Howard W Sams amp Co pp 11 32 ISBN 0 672 22456 9 Basic Commodore information permanent dead link Rupert Dale July 1987 Rupert Report Computers in Control Ahoy New York Ion International p 32 ISSN 8750 4383 Retrieved 2018 04 12 pinouts ru C64 Cassette pinout 2012 01 15 Commodore 64 Programmer s Reference Guide West Chester Commodore Business Machines 1984 Commodore 64 Schematic Diagram ISBN 0 672 22056 3 Retrieved 2018 04 12 SAMS Computerfacts CC4 Computer Commodore 64 Indianapolis Howard W Sams 1984 p 2 a b c d How Commodore tapes work 091205 wav prg sourceforge net Datasette service manual model C2N 1530 1531 preliminary Oct 1984 PN 314002 02 http www zimmers net anonftp pub cbm faq trivia cbm trivia 13 txt bare URL plain text file Abril Editora 26 October 1973 Placar Magazine Editora Abril Retrieved 27 June 2017 via Google Books Bo Zimmerman Commodore Datasettes Commodore Gallery Retrieved 20 April 2012 Thornburg David D April 1981 The Commodore VIC 20 A First Look Compute p 26 Butterfield JIm April 1981 Advice to PET Owners How To Be A VIC Expert Compute No 11 p 34 Anderson Chris June 1985 On top of the US Goldmine Zzap 64 interview pp 46 48 Retrieved 26 October 2013 Pountain Dick January 1985 The Amstrad CPC 464 BYTE pp 401 Retrieved 27 October 2013 Halfhill Tom Dec 1983 The Editor s Notes Compute s Gazette editorial p 6 Retrieved 6 February 2016 Wagner Roy August 1986 The Commodore Key Computer Gaming World p 28 Retrieved 1 November 2013 Brooks M Evan November 1987 Titans of the Computer Gaming World MicroProse Computer Gaming World p 16 Retrieved 2 November 2013 External links editSimilar Commodore tape drives Datasette photos Description of tape format with conversion utilities and code C2N232 project to build a hardware adaptor software program to archive Commodore Datasette files to a modern computer DC2N Homepage Digital C2N replacement project Sketchup model of the Commodore Datasette 1530 Sketchup model of the Commodore Datasette 1530 Retrieved from https en wikipedia org w index php title Commodore Datasette amp oldid 1174256259, wikipedia, wiki, book, books, library,

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