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Donn Stewart
13917 Deviar Dr
Centreville, VA 20120
dstew@cpuville.com

Designing, Building, and Selling Obsolete Computers -- for Educational Purposes -- since 2004

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News and Issues

November 9, 2017: PCGET and PCPUT file transfer utilities for CP/M on the CPUville Z80 kit computer

For those of you who have CP/M 2.2 running on the CPUville Z80 kit computer, you have no doubt noticed that adding files to the CP/M system from the PC is a bit awkward. One has to use the CP/M program MONITOR.COM to do a binary transfer of the file into the computer memory, then the CP/M built-in command SAVE to store the file onto the CP/M disk. I had sought to use any of several XMODEM-type CP/M programs to do file transfers, but they all required a system with two serial ports, one for the terminal, and one for a modem to do the file transfer.

However, customer Stephen Williams has modified two XMODEM CP/M utilities to perform file transfers from the PC to the CPUville Z80 kit computer over the single serial port. These utilities, PCGET and PCPUT were created by Mike Douglas for his Altair 8800 Clone computer. He derived them from the original XMODEM-based file transfer utilities created by Ward Christensen in 1977 for his early bulletin board systems. With the permission of both Mike Douglas and Stephen Williams I have placed the code for these utilities on the CPUville CP/M code page for download.

PCGET will transfer a file from the PC over the serial interface onto the CP/M disk, and PCPUT will transfer a file from the CP/M disk to the PC. To do this, one must be using a terminal emulation program with the ability to do XMODEM-protocol file transfers. In the Linux environment, minicom will do this. In the Mac environment, the serial program will work. In Windows however, the Realterm program recommended for use with the CPUville Z80 kit computer does not do XMODEM transfers. Instead, use the ExtraPuTTY program.

One last thing: to get PCGET.COM onto the CPUville computer you will have to do the MONITOR.COM binary transfer and CP/M SAVE procedure, as explained in the disk and memory expansion kit instructions. After that, you can use PCGET to do file transfers.

September 16, 2017: A new CPUville website

You probably noticed that I have redone the entire website. I made these improvements:

Let me know if you like it. Feel free to suggest improvements. If you find errors, or broken links, please let me know.

June 3, 2017: 8-bit processor prototype

I have finished the 8-bit processor prototype. It is working well. Here is a demo video:

Note that the processor is connected by an adapter to the CPUville Z80 computer system board, plugged into the Z80 socket. I plan to put details of the design and construction of this processor on the web site in the future.

April 7, 2017: Problem with 2K RAM ICs

It has come to my attention that some 6116 2K RAM ICs that have been shipped with the CPUville Z80 computer kits may be defective. You can test yours by running the memory test program, located at 0x0074 in the v.7 EPROM. If you believe you have a defective 6116 RAM IC please let me know, and I will send you a replacement.

March 22, 2017: A new processor

I am developing an 8-bit computer processor that I may offer as a kit.This processor is similar to the original CPUville TTL processor, with some important differences. First, it has an 8-bit data bus, and a 16-bit address bus (that is, a 64K address space), matching the Z80's data and address bus. This means it can use the same system as the CPUville Z80 computer, by plugging into the Z80 slot on the computer kit board (using a cable of course). Second, I fix some of problems with the original processor, in main, that the ALU size did not match the instruction size, preventing easy uploading of programs. Instructions on the 8-bit processor are of varying length, instead of the single size of the original processor. Also, I have strengthened some of the hardware issues, for instance, latching the controls that need to be held steady when the state changes for writing memory or ports. A kit for this processor may cost $80 to $100. Anyone interested?

November 14, 2016

hand holding an EPROM

Tiny BASIC! In discussion with another hobbyist I realized I could assemble Tiny BASIC and it would fit into the CPUville Z80 computer 2K ROM space, taking the place of the v.7 EPROM. I made a few modifications to the code to match the CPUville computer's port addresses and UART status bits, and it works fine:

screen image of tiny basic program output

This is Li-Chen Wang's original Tiny BASIC that was first published in Dr. Dobb's Journal of Computer Calisthenics and Orthodontia in May, 1976. Here is a link to a draft of the instruction manual I am preparing. If you would like the code, please email me. I can also sell you a pre-programmed EPROM with Tiny BASIC for $4.50.

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