Hardware, RC2014, Homebrew Z80 Computer


Building my own Z80 Computer

I've had the computer kits lying around for a year now. Now the time has come. Weekend. The weather is getting worse outside and there isn't much left to do in garden. Building the Z80 starts on 27.09.2019 and ends on ... see below ...

Assembling the modules 1 to 7 I finally needed one week (after work), whereby I did nothing for two days.

I don't know what to say. The system is simply ingenious and relatively easy to assemble/solder. Congratulation to Spencer Owen!
RC2014 booting
Boot-up process: RC2014 Zed Pro

My RC2014 Zed Pro

Runs RomWBW (v.2.9.1-pre.5, 2018-08-29) with the CP/M 2.2 operating system and also the Z-System. Update: 19.10.2019, v2.9.2-pre.15.

  1. Backplane Pro ............... (27.09.2019, 28.09.2019)
  2. z80 2.1 CPU Module .......... (29.09.2019)
  3. 512k ROM 512k RAM Module .... (29.09.2019)
  4. Dual Serial SIO/2 Module .... (29.09.2019)
  5. Dual Clock Module ........... (29.09.2019)
  6. Compact Flash Module ........ (02.10.2019)
    • If you use the compact flash module AND the IDE module at the same time on the RC2014 beware that drive C: und D: are assigned to IDE0:0 and IDE0:1 (CF-card) and drive E: to H: to PPIDE0:0 und PPIDE0:1 (hard disk)!
    • Of the 8 possible CF-card CP/M slices, only the first two can be used. The remaining 6 are still present but not visible and cannot be used.
    • Personally, I prefer to work only with the CF card. I divided my 48 MByte card into five CP/M slices (8 MByte each) and a 6 MByte FAT12 DOS partition. With the FAT partition you can exchange files between your PC and RC2014 with FAT.COM.
  7. DS1302 Real Time Clock ...... (04.10.2019, designed by Ed Brindley)
    • If the RTC is not plugged in, then the boot process takes about 72 seconds. The RC2014 queries the RTC for the time. If it doesn’t get a reply, it waits for a timeout, and then boots up.

  8. Digital I/O Module .......... (10.10.2019)
  9. Pi Zero Serial Terminal ..... (not yet assembled)
  10. IDE Hard Disc Module ........ (06.10.2019, designed by Ed Brindley)
  11. ESP8266 Wi-Fi Module ......... (19.10.2019)
    • Wi-Fi is working, but Telnet and the serial link not; maybe a problem with the terminal setting! To be continued ...
  12. YM2149 Sound Card Module .... (10.11.2019, designed by Ed Brindley)
  13. Universal Micro Keyboard .... (not yet assembled)
  14. Floppy disk controller ...... (08.11.2019, designed by Dr. Scott M. Baker)

RC2014 Zed Pro
Assembled RC2014 Zed Pro

Special features ...

... to be observed during operation

To be improved

... File transfer

The operation of the terminal connection with a PC works fine with 115.200bps, but the file exchange with XMODEM sometimes failed.

06.10.2019: Problem solved, see workaround part 3 and/or 4!

A possible solution (not yet tested): XMODEM Baud Rate Mod for RC2014.

Otherwise only the program DOWNLOAD on the RC2014 can be used. But this possibility is extremely slow and not reliable, at least for me. Have a look at Grant Searle: How to install applications.

Here are my workarounds. All solutions work flawlessly.

Workaround (part 1): Changing clock frequency

You have to change the clock frequency by setting the jumper of CLOCK 1 not to 7.3728 (115.200pbs) but to 0.6144 (9.600bps). The whole RC2014 will be 10 times slower, just 0.61 MHz. However, this means that you can now easily copy files from the PC to the RC2014 with XMODEM. This now works fine at 9.600bps. Once you have copied all files, jump back to 7.3728 MHz and restart the RC2014. That was it already.
Workaround (part 2): Using FAT.COM (Wayne Warthen)

This little inconspicuous program is awesome! You first have to prepare a CF card with FDISK80.COM for both CP/M slices and a primary DOS partition. Then initialize with CLRDIR and finally format the DOS partition on the PC. Then insert the CF card back into the RC2014 and reboot. Now you can access the DOS partition with FAT.COM from CP/M, i.e. also copy files. File exchange is no longer a problem. Simply copy the CP/M files to the CF card under DOS and then copy them to the CP/M slice under RC2019 (CP/M).
Workaround (part 3): Using a RAM disk

So far I have always saved the download to the RC2014 on the CF card. But there is also the RAM disk. See there, it works perfectly. My settings: 115.200 bps, 8 data bits, no parity, 1 stop bit and hardware flow control. Finally you have to copy the files to the CF card! Otherwise the files will be lost when restarting.
Workaround (part 4): Using the RC option

Use XM with the option RC: A>B:XM RC TEST.COM

Now the checksum protocol is selected within XM, the transfer should work from PC to ZETA V2 or RC2014.

A few impressions

Turbo Pascal 3.0a
Turbo Pascal 3.0a on the RC2014

I loaded the example program CMDLIN.PAS, compiled it to the CF card and started it. Everything is fine.

Wordstar 4
Wordstar 4 on the RC2014

I loaded the text file SAMPLE.TXT. Everything is fine. You are looking for a good text editor? Try Wordstar in non document mode. Simply good! Only the vi under UNIX is better :-)

External links