Description

Vintage collectors and enthousiasts will know the TMS 7000 processor from the CC-40 home computer and the TI-74 calculator. Currently the TMS70C02 chip, the latest generation of this line, is cheap and available on-line. Reason enough to create a new board to play with the processor and write some assembly code.

The first phase will be a single processor board with ROM and RAM, which uses the internal serial port and the internal serial port with a monitor as interface.

The second phase will add a 6-hex-digit LED display and hex keyboard, similar to the Kim-1 and Microprofessor MPF-1.

An other goal is to use and evaluate the ROM-Emulator as a fast development tool for the firmware, being the serial monitor and later the hex display & keyboard.

The software side of the project will be stored at github: https://github.com/electrickery/TMS70C02-Monitor/tree/main

Project Logs

Almost the Arduino development model

(08/01/2024 at 19:37)

With support to both the Arduino firmware and the RomEmulatorTerminal script of a 'download-relay' it is possible to have a 'hands-off download' operation, where the target processor is held in RESET during download. For ROMs intended during startup, this makes firmware development almost as simple as the Arduino environment.

On the image are all relevant components strapped to a carton board and connected to a USB hub. The ROM-EMulator is conencted to the boot-ROM and the target board output is currently the serial port. Even the board is powered via USB. By bridging the RESET switch of the target board with the relay, the processor is halted until the ROM download is completed.

The Arduino sketch and download application script can be found are the ROM Emulator github project page: https://github.com/electrickery/ROM-emulator

First stable monitor version

(08/06/2024 at 09:43)

The code is now more or less complete for now at version 0.3.2. The command naming might change and the Intel-Hex download isn't implemented yet. Here is the current help text, which summarized the command list:

** TMS70C02 Monitor Help Menu V0.3.2 **

         Caaaa - Call subroutine at aaaa
         D[||+|-|aaaa[-bbbb]] - Dump memory from aaaa to bbbb
         E[e] - View/set echo
         Faaaa eeee dd - Fill memory from aaaa to eeee-1 with dd
         Gaaaa - jump to address aaaa
         Maaaa bb - Modify memory location
         H - Help menu
         Raaaa eeee - RAM test from aaaa to eeee
         Vssss eeee nnnn - Copy memory range ssss to eeee to nnnn
        *:ssaaaattdddddd....ddcc - receive Intel-hex record
         * = not yet implemented

 See the complete code and resulting binaries (bin & hex) at the github site: https://github.com/electrickery/TMS70C02-Monitor

Interrupt routine (and display) working!

(09/15/2024 at 12:40)

After quite some time reading and coding and fixing I managed to get some text on the display. The display (and later keyboard) routine is triggered by interrupt and runs along side of the serial monitor, which is completely based on polling the serial port. The displayed patterns were actually poked in the display buffer using the the serial monitor.

Display & keyboard routines (and hardware fixes)

(09/18/2024 at 09:16)

The key scan is now working as it should, the key value to display pattern routine too. This startup pattern should scroll to show the remaining 'C02' characters of the message, but that is a ToDo item. Now functions should be assigned to the keys, at least for the values 0-F, memory, up, down, ... Most inspiration will probably come from the MikroKit09 and MPF-I.

Project reposted with permission. If you want to explore more projects, please follow the author: fjkraan (Hackaday). He has many wonderful projects and is an excellent maker. Enjoy it! :)