TK85

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TK85
DeveloperMicrodigital Eletrônica
ManufacturerMicrodigital Eletrônica
TypeHome computer
Release date1983; 41 years ago (1983)
Operating system8K Sinclair BASIC
CPUZ80 @ 3.25 MHz
Memory16 or 48 KB
Removable storageExternal Compact Cassette recorder at 300 or 4200 bps
DisplayMonochrome display on television; 24 lines × 32 characters or 64 × 48 pixels graphics mode
GraphicsDiscrete logic circuits
Power9V DC
Backward
compatibility		ZX81
PredecessorTK83
SuccessorTK90X

The TK85 was a ZX81 clone made by Microdigital Eletrônica, a computer company located in Brazil.[1][2][3] It came with 16 or 48 KB RAM, and had a ZX Spectrum–style case, similar to a Timex Sinclair 1500.[4][5]

Unlike the ZX81, the TK85 used standard logic components rather than a gate array ("ULA"), and during manufacture several of them were scraped so that competitors couldn't easily copy the circuit. The circuit board had space for a AY-3-8912 sound generator chip (compatible with the ZonX-81 sound board), and although none came factory installed, it is possible to add the necessary circuits.[6]

The TK85 came with a copy of the 8K ZX81 floating point BASIC, and an additional 2K EPROM, mapped to addresses 8192-10240, containing machine code routines for use with tape files. These routines could save with HISAVE, load with HILOAD and verify with HIVERIFY in "Hi-Speed" (4200 bps);[5] save and load, BASIC variables in 300 bps (standard ZX81 speed) using SAVE and DLOAD functions and 4200 bps (Hi-Speed) using DHSAVE and DHLOAD. These routines were all accessible using RAND USR commands. The save to variable function could be used to make copies of programs on tape.[2]

The expansion port on the back of the computer is compatible with the ZX81, although some peripherals may not work due to conflicts with the 2K of extra ROM.

The rear of the computer featured a TV output (without video back porch), "EAR" and "MIC" sockets for connecting to an external tape recorder, a joystick port using a DIN socket (that simulated the 5,6,7,8 and 0 keys), a ZX81 compatible expansion port, space for a sound output socket, and a socket for the 9V external power supply.

Since the joystick used the cursor keys, and due to the circuitry for the keyboard, it wasn't possible to detect diagonal directions correctly.

References

[edit]
  1. ^ "Micro TK 85 - ZX81". COB-Clube Old Bits. 2008-07-26. Archived from the original on 2008-07-26. Retrieved 2022-12-19.
  2. ^ a b TK85 - Programação BASIC (PDF) (in Brazilian Portuguese). São Paulo, Brasil: Microdigital Eletrônica Ltda. 1983.
  3. ^ "TK 85". MUSEU DE COMPUTAÇÃO PROFESSOR ODELAR LEITE LINHARES (in Brazilian Portuguese). UNIVERSIDADE DE SÃO PAULO - INSTITUTO DE CIÊNCIAS MATEMÁTICAS E DE COMPUTAÇÃO. 2023.
  4. ^ "Computador TK 85". Museu de Tecnologia da Unoeste (in Brazilian Portuguese). 13 June 2016. Archived from the original on 2022-12-19.
  5. ^ a b "TK-85 Microdigital". www.old-computers.com. Archived from the original on 2022-01-29.
  6. ^ Murta (2010). "Instalando o PSG AY-3-8912 no TK85". ZX81 Never Die.
[edit]
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