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I integrated the TRS-80 Model I ROMs into my MCLZ8 Z80 emulator and mapped the UART to the TRS-80’s keyboard and video RAM and now have it running on a standalone Teensy 4.1 board! TRS-80 MODEL I EMULATOR USES MCLZ8 IN A TEENSY

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I have four boards to give away, so if anyone wants one please send me a message. You would need a Teensy 4.1 and also do a bit of soldering for your choice of connectors.

Project files are now on GitHub: MCLZ8 Github

In acceleration mode-3 the MCLZ8 appear to be 15-20X faster than the stock Z80, which is much too fast for the disk drive to work properly. The keyboard also has difficulty debouncing so you get multiple letters per keystroke. The MCLZ8 is written in C so we could add code to enable/disable acceleration around IO functions like disk and keyboard accesses. But I would need the TRS-80 community's help on this! If someone could give me the memory/IO accesses to look for, I can certainly add this functionality. I just received my TRS-80 Model III from eBay last week, so Im not very familiar with it's inner-workings yet

No plans to sell them, but I the short term I will give away some of the first batch of the boards. It cost me only $25 for five of them including shipping! I will upload the project files today so anyone can build one of these boards. The files for the MCL65+ are already on GitHub. I will also try to figure out how to make the PCB available from JLCPCB so that you only need to select it as a pre-made project.

I posted some videos of a few games and also a quick demo of the degree of acceleration achieved with the MCLZ8. Posted on my blog here: MCLZ8 VIDEOS – GAMES AND Z80 ACCELERATION

Below is a snapshot of running tthe MCLZ8 at the command-line. It would be easy to add this to the hardware version so you could set a breakpoint, then go into single-step mode which would dump registers, flags, and anything else of interest. True. I have done this, and was thinking of trying different ROMs on my Model III for fun. One could also make some testing code which exercises all of the TRS-80 motherboard components from the Z80 CPU's slot. I have done this already for the Commodore 64: COMMODORE 64 TESTER USING MCL64 Yes, I use the USB UART supplied by the Teensy and use the Arduino Serial.xxx function calls. Easily done.. Just a UART keystroke or an access to specific address could cause the MCLZ8 to stop the emulation, dump the CPU state and any memory ranges you wish.

Thanks! Yes, having break points, register dumps, and single-stepping are easily done. In-fact, thats how I developed this core! I debugged the MCLZ8's Z80 core using a command-line version on my laptop where a register dump was done after each opcode. I then ran my core in lockstep with a known-working Z80 emulator - stopping on any difference between the PC, registers or flags. I then ran the ZEXALL opcode test to dial-in the Z80 correctness. All that was left after that was to add some code for the Bus Interface Unit (BIU) which toggled the Teensy's GPIOs to emulate the Z80's local bus interface. Oh, and of course build a PCB which contains some buffers to translate the 5V Z80 signals to the Teensy's 3.3V. Ill post all of this on GitHub shortly... Acceleration speed wasn't the goal of this project... Just a cool side-effect! The goal was to write my own Z80 emulator which can be used as a drop-in replacement for the original CPU.

My board is taller than it needs to be... I have an extra socket on the motherboard side to protect the original one, and I have sockets for the Teensy which are raising it up a good deal. If you skipped both sockets the MCLZ8 would be significantly shorter. Similar to any of the other vintage TRS-80 accelerator boards.

I wanted to share my latest project, the MCLZ8, which is a Zilog Z80 emulator which can be used as a drop-in replacement for the original Z80. My recent Wordpress blog entries can be found here: MCLZ8 – ZILOG Z80 EMULATOR IN TRS-80 MODEL III MCLZ8 – TESTING VARIOUS APPLICATIONS I will post some videos shortly which demonstrate running the MCLZ8 in cycle accurate and accelerated modes where it appears from initial testing that it can run 15X faster than the stock Zilog Z80! Thanks, -Ted

I posted a few copies of the EPROM Emulator on eBay: https://www.ebay.com/itm/154425061318 And of course the project is open-sourced, so you can build your own: https://github.com/MicroCoreLabs/Pro...EPROM_Emulator

Yup, totally works... (for systems like the IBM XT) The OE_n signal is attached to the output enables of the data buffers, so it does not corrupt the bus. For for systems that use separate OE_n and CS_n like the PCjr will need a jumper wire. It was a proof of concept which was fun and inexpensive to make. Five boards were made, so im gauging the interest in building more... Improvements could include supporting both CS_n and OE_n, pinouts for pre-EPROM devices, or multiple chip-selects so a single board can support multiple socketed ROMS.

Hi, I thought I would share my small EPROM Emulator project: Link to EPROM Emulator Project It's a little smaller and simpler than some of the other EPROM emulators, so maybe someone could find useful. Thanks, -Ted