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108 lines
6.8 KiB
Markdown
108 lines
6.8 KiB
Markdown
# TK2000 Disk Interface REDUX
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## DISCLAIMER
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Any use of this project is **under your own responsibility**.
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You will be responsible of checking the correct construction and functionality of your board.
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By using this project You will agree that I cannot be held responsible if it will destroy any of your devices, damage your computer, burn down your house or whatever.
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### Sponsorship
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This project is kindly sponsored by [PCBWay](https://pcbway.com).
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PCBWay specializes in manufacturing high-quality PCBs and makes them affordable to hobbyist and professionals alike.
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The range of services they offer include PCB prototyping, assembly, instant quotes for your order, a verification process by a team
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of experts and an easy to use, hassle-free order process.
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I'm grateful to PCBWay for the help in evolving and testing this project. You can order the currently released revisions of the board from them, see the link below!
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## Introduction
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The TK2000 had a floppy disk adapter that came in form of a cart, connected directly to the computer, and supported only a single drive connected to it.
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Luckily, the adapter was nothing more than a ripoff of the original Apple Disk II interface with some changes to adapt it to the TK2000 bus, so, starting with the
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[recreation by btb](https://github.com/btb/DiskII) as a base, I converted the original interface back to the TK2000, gaining support for a second floppy disk and
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configurable (via jumpers) I/O and ROM addresses.
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This board is meant to be used in the [TK2000 bus extender](https://codeberg.org/hkzlab/TK2000_bus_extender) and is part of my project to build a set of cards for the TK2000 computer.
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You can build yourself a TK2000 computer using files from [this repo](https://github.com/clemarfolly/Microdigital-TK2000) and following my [build notes](https://github.com/hkzlab/TK2000_Build_Notes).
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## Hardware
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The board was designed with [KiCad](https://kicad.org/) EDA.
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### Bill of Materials
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| Component | Qty | Type / Value | Notes |
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| ---------------------- | --- | ------------------------------------------------------- | -------------------------------------------------------------------- |
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| U1, U2 | 2 | 74LS138 DIP-14 | |
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| U3, U8 | 2 | 27C32/64/128/256/512 | Any of these EPROMS will work, as long as the access time is <=100ns |
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| U4 | 1 | 74LS259 DIP-16 | |
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| U5 | 1 | 74LS05 DIP-14 | |
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| U6 | 1 | NE555P or compatible DIP-8 | |
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| U7 | 1 | 74LS132 DIP-14 | |
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| U9 | 1 | 74LS323 DIP-20 | |
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| U10 | 1 | 74L174 DIP-16 | |
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| Q1 | 1 | 2N3096 TO-92 | |
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| C1, C9 | 2 | 22uF/16V+ 2.5mm electrolytic capacitor | |
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| C2 - C8 | 7 | 100bF/25V+ 5.0mm ceramic caps | |
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| J5, J6 | 2 | 2x10 2.54mm pin header, right angle | |
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| J2, J3 | 2 | 2x8 2.54mm pin header, straight | |
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| J1, J4 | 2 | 1x2 2.54mm pin header, straight | |
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| R1, R6 | 2 | 10K ohm, 1/4W resistor | |
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| R2 | 1 | 560 ohm, 1/4W resistor | |
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| R3, R4 | 2 | 2.7K ohm, 1/4W resistor | |
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| R5 | 1 | 47K ohm, 1/4W resistor | |
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| R9 | 1 | 3K ohm, 1/4W resistor | |
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#### The ROMs
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The ROMs have the first 8 address lines (A0-A7) connected to the bus, A8 is connected to a pull-down resistor and can be forced high using J1 for U3 and J4 for U8.
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All the remaining address lines are connected directly to VCC, which means that, following the proper pin alignment, EPROMS from 27C32 to 27C512 can be used.
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The original Disk II card used biproms 256 bytes in size, so the dumps needs to be properly concatenated before being used in this card.
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If you wish to use 27C512, you can find pre-made files in the `ROMs` directory (the files used in these are property of Apple).
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- U8 houses the content of the P6 ROM
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- U3 houses the content of the P5 ROM
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Using the premade files will have the 13-sector image loaded when jumpers on J1 and J4 are not installed, and the 16 sector image loaded when the jumpers are installed.
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### Configuring the address
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The address for the I/O ports (DEVICE SELECT) can be changed by jumpering J3.
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```
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J3: DEVICE SELECT
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C C C C C C C C
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0 0 0 0 0 0 0 0
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8 9 A B C D E F
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x x x x x x x x
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^ default
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```
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The address for the ROM (I/O SELECT... confusing, I know) can be set by jumpering J2.
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```
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J2: I/O SELECT
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C C C C C C C C
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1 3 5 7 9 B D F
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x x x x x x x x
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x x x x x x x x
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^ default
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```
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The defaults are marked on the board.
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### Ordering the boards
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You can order the board for this project at [PCBWay](https://www.pcbway.com/project/shareproject/TK2000_Disk_Drive_Interface_4ec79fd6.html) and support me or download
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the gerbers and have them printed wherever you like!!!
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