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Platinum7 Electronics


What is on the cards?

I am designing a TRS-80 Model 1 Clone.  My first computer was a TRS-80 Model 1 I bought while working at Tandy Electronics (the Australian version of Radio Shack) when I was 15 and I thought that would be a great addition to recreate.

I am adding a lot of extra features that make it a bit more special:

  • Full 48K memory (switchable to 4K or 16K if required)

  • Level II ROM switchable with Level I if required

  • Variable clock speeds up to 8MHz

    • Initially it will boot at the standard 1.774MHz and the speedup frequency can be chosen from 1.5x (2.661MHz), 4MHz, 3x (5.332MHz) or 8Mhz by using a rotary switch.  To make the CPU use the higher speed, do an OUT 254, 1 or OUT 254, 0 for normal​ speed.  This is the standard way for the speedup modifications of the time

  • Monochrome VGA output (800x600)

    • It will still be exactly the same 64x16 character display with the chunky graphics, however on a VGA screen, not a composite monitor

      • This is using an ATF1508 CPLD for the timing​

    • It has a dual ported memory for the video memory so the screen tearing of yesteryear will stay a thing of the past

    • It will have the standard Tandy lower case "conversion" as standard as 8 bit memory is a lot cheaper now!

    • There will be a selectable second font that uses more pixels, so gives a smoother look.

  • Standard Cassette output/input for storing software

    • Can be used with modern devices (PC as a recorded/player or a digital recorder)

    • I am going to add a Data Dubber to allow for correct loads as much as possible from old tapes

  • Inbuilt Audio amp so you can get the sound from the games or listen to the tapes loading/saving

  • A full keyboard with modern Cherry (or compatible) keys - I am working on a way to get reasonably priced custom keycaps

  • RS232 using a modern UART and the ATMEGA328P to translate the commands with both a USB and a standard 9-pin male D plug

  • Real Time Clock emulating the NewClock-80 (using a modern RTC controlled by the ATMEGA328P)

  • Orchestra-80 compatible stereo output
  • Joystick interface for Atari compatible Joysticks emulating the Alpha Joystick

  • Printer interface that works the same as the one in the Expansion Interface, however comes out on a DB25 connector to allow for IBM Compatible cables or a 34way header for a simple cable

It will have the standard 40 way card edge connector on the back so you can add external plugin devices and hopefully the standard expansion interface as well (the clone's internal printer interface and 40Hz heartbeat interrupt that come from the expansion interface will need to be disabled with a switch).

And the edge connector will have _GOLD_ plating so no more corrosion!  I can also supply a spare one for your Expansion Interface connector.

I am going to investigate adding either of these to the main board

  • Floppy Controller (using new old stock for the FD1771 and FD1772) with Data Separator

  • Floppy Emulator which uses an SD card for storage

It will probably be the emulator as that would look like an FD1771/2 to the Operating system, however it would use modern technology that is readily available.

All the above will be designed with as many through hole devices as I would like to sell as a kit and make it easier to solder.

The ATMEGA328P chip will control a small OLED display showing current CPU speed and other information or some lovely matrix LEDs (LTP-305) spelling out the speed.  It will also control the modern UART to translate the commands from the old UART chip used in the TRS-80 to the modern one I am using, as well as emulating the commands for the NewClock-80 Real Time Clock. 

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