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A 4$, 4ICs, Z80 homemade computer on breadboard

No iron, no cry! Build a mini 4MHz Z80 64kB RAM system with Basic and Forth interpreters, CP/M 2.2, QP/M 2.71, Assembler and C toolchains

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This is the Z80-MBC (Mobile Breadboard Computer), a mini 4MHz Z80 64kB RAM system with Basic and Forth interpreters, CP/M 2.2, QP/M 2.71, Assembler and C toolchains.

It is a complete development "ecosystem", and using the iLoad boot mode it is possible cross-compile, load and execute on the target an Assembler or C program with a single command (like in the Arduino IDE).

More, it can be easily expanded and it has an "Arduino heart" using an Atmega32A as an "universal" I/O emulator, and can be used and powered with a tablet or smartphone too...

This project has grown a lot on the way (more than I've supposed at the beginning...) and now is renamed as "Multi Boot Computer" and is available on PCB (thanks to Bill Westfield) too.

In the "Instructions" section there is a quick building guide updated to the last developments.

In the "Files" section there are the components list and BOM for both the versions.

During some surfing on Ebay I realized that with 4$ it is possible to buy enough ICs to build a complete Z80 system that can be done using a breadboard, and taste some flavor of retro computing.... So I did it and here it is the story!

Here is a video with the Z80-MBC in action:

and here with a smartphone (so it is explained the word "Mobile" in his name...) with a common OTG cable (the various test clips in this video were used for some measurements with a Logic Analyzer):


* * HARDWARE OVERVIEW * *


The needed ICs are:

  • Z80 CPU CMOS (Z84C00) 4Mhz or greater ($1.16)
  • Atmega32A ($1.70)
  • TC551001-70 (128kB RAM) ($1.10)
  • 74HC00 ($0.25)

Total cost: $4.21

The wires were taken from salvaged broken LAN cables, and the other components were salvaged from others unused breadboards.

The schematic is attached in the Files section. The MCU Atmega32A is used as universal I/O subsystem, as Eeprom, and as reset and 4MHz clock generator for the Z80 CPU.
Into the Atmega32A it is flashed an Arduino bootloader taken from here , and it is possible to use the Board Manager of the Arduino IDE for that.

Flash the Arduino bootloader at first (with the method you prefer), next you can start to build the whole thing!


Of course I used the Arduino IDE to develop the IOS (I/O Subsytem) that interacts with the Z80 bus and "virtualizes" the peripherals seen by the Z80 CPU.
As oscillator it is used the internal 8MHz Atmega32A oscillator, so no quartz is needed, and from this one is derived the 4MHz clock for the Z80 CPU (so the "Internal 8MHZ osc." bootloader variant must be chosen when flashing the bootloader from the Arduino IDE!).


The 74HC00 is mainly used as RS flipflop to stop the Z80 CPU during I/O operation, giving the needed time to the Atmega32A to interact with the Z80 bus.
The 128kB RAM TC551001 is used only for half (64kB) because the Z80 address space is only 64kB (I've chosen this IC for the low cost).
Note that only the CMOS version of the Z80 CPU can be used here. This because only CMOS version, under given condition that are respected in this schematic, has logical levels compatibles with Atmega32A and 74HC00.


NOTES ABOUT THE COMPONENTS:


You can use any Z80 CMOS speed grade, because the lowest is 4MHz.
The 74HC00 can be substituted with a 74HCT00 if you already have one.
The RAM chip TC551001-70 can be substituted with any suitable 64kB RAM (do not use < 64kB RAM).
The USER led (D5 in the schematic) MUST be blue or white just to be sure that V(forward) is >= 3V.


Here is a video that shows a simple basic program that interacts with the "USER led" and "USER key":



On the breadboard there are others status led: the HALT led turns on if an HALT instruction is been executed and the Z80 CPU is in a Halt state, the DMA led turns on during DMA operations when the Z80 bus is in Hi-Z, the IO_OP led turns on when the Z80 CPU is accessing a I/O virtual device "emulated" by the Atmega32A (as the serial port), the LED_D0 led is the classical "Arduino" led (that one connected to D13 pin on the Arduino Uno) that here is connected with the Arduino D0 pin and is turned on normally as a power on indicator.


The serial port SERIAL-USB (see schematic) can be connected with a TTL-RS232 adapter, or with a serial-USB adapter.
I've used a serial-USB adapter that acts also as power source for the Z80-MBC, and has the DTR signal for the "autoreset" driven from the Arduino IDE. For a terminal that has a serial TTL port no adapter is needed.


In the schematic there is also the IOEXP port to expand the I/O capabilities, i.e. adding GPIO ports or a RTC for future expansions.


* * SOFTWARE OVERVIEW * *


I've "ported" the Basic interpreter to the Z80-MBC using the sources provided in the great Grant Searle site ,...

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Z80-MBC PCB version - BOM.xls

Component list and BOM for the Z80-MBC PCB version (see schematic and gerbers at: https://github.com/WestfW/4chipZ80)

ms-excel - 28.50 kB - 10/17/2017 at 07:05

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Z80-MBC - BOM.xls

Component list and BOM for the Z80-MBC on breadboard

ms-excel - 28.50 kB - 10/17/2017 at 07:04

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SRecord-custom.zip

Batch and custom files for SRecord utility to make custom virtual disk images.

Zip Archive - 16.06 kB - 05/29/2017 at 15:03

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CPMtools-custom.zip

Batch and custom files for CPMtools utility to make custom virtual disk images.

Zip Archive - 4.48 kB - 05/29/2017 at 15:02

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S221116_R110517_Z80.ino

The sketch for the Atmega32A (New release. Adds the QP/M 2.71 and RTC support).

x-arduino - 167.77 kB - 05/23/2017 at 19:21

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  • 1 × For the breadboard version see the file "Z80-MBC - BOM.xls" in the Files section
  • 2 × For the PCB version see the file "Z80-MBC PCB version - BOM.xls" in the Files section

  • How to make custom Virtual Disk images

    Just4Fun05/29/2017 at 14:29 1 comment

      To do that you need two really powerful tools: Cpmtools to create CP/M disk images and SRecord to manipulate ROM/EPROM images.
      Take in account that the structures of the virtual disk 0 and 1 of the Z80-MBC are different. Disk 0 has the two first tracks reserved for the system image (loaded into RAM by the CP/M loader), instead disk 1 doesn't have this "reservation". This means that the images have a different "structure". More, because disk 0 must have the system image inside the two first tracks, the disk 0 image creation will be different if the OS is CP/M rather than QP/M.
      So to make things easier I've prepared some batch file to simplify the needed operations.
      As for the Assembler and C toolchains you need a Windows host or VM.


      Here all the steps to set up the needed tools:

      1. Create a working directory on your Windows Machine;
      2. Download Cpmtools and unzip in your working directory;
      3. Download last version of SRecord and unzip in your working directory;
      4. Download from the Files section CPMtools-custom.zip and unzip the files into the directory containing the Cpmtool executables (as cpmcp.exe). During the copy overwrite the file DISKDEFS because the new one contains the needed definitions for the Z80-MBC;
      5. Download from the Files section SRecord-custom.zip and unzip the files into the directory containing the SRecord executables (as srec_cat.exe).

      Now you are ready to create your custom image. First create a sub-directory (called e.g. CPM-files) in the cpmtools directory to store all the files to load in the disk image. Check that they fit into the 128kB avaliable space.


      Steps to create a Disk 1 image

      1. Go to the cpmtools directory and with an editor modify/add/delete in the file MakeDisk1.bat the various lines "cpmcp -f z80mbc-d1 %dskfile% CPM-files\xxxxx.yyy 0:xxxxx.yyy" to match the directory in your host (if needed) and all the files to load (xxxxx.yyy);
      2. From the cpmtools directory open the provided DOS command shell and give the following command (I'll use here the name disk1.dsk for the disk image file):
        MAKEDISK1 disk1.dsk
      3. After the execution copy the file disk1.dsk in the SRecord directory;
      4. Go to the SRecord directory, open the provided DOS command shell and give the following command:
        D1TOHEX disk1.dsk
      5. After the execution you will find four files named from disk1_SEG0.hex to disk1_SEG4.hex to upload into the virtual disk with iDisk.


      Steps to create a Disk 0 CP/M image

      1. Go to the cpmtools directory and with an editor modify/add/delete in the file MakeDisk0CPM.bat the various lines "cpmcp -f z80mbc-d0 %dskfile% CPM-files\xxxxx.yyy 0:xxxxx.yyy" to match the directory in your host (if needed) and all the files to load (xxxxx.yyy);
      2. From the cpmtools directory open the provided DOS command shell and give the following command (I'll use here the name disk0CPM.dsk for the disk image file):
        MAKEDISK0CPM disk0CPM.dsk
      3. After the execution copy the file disk0CPM.dsk in the SRecord directory;
      4. Go to the SRecord directory, open the provided DOS command shell and give the following command:
        D0TOHEXCPM disk0CPM.dsk
      5. After the execution you will find four files named from disk0CPM_SEG0.hex to disk0CPM_SEG4.hex to upload into the virtual disk with iDisk.


      Steps to create a Disk 0 QP/M image

      1. Go to the cpmtools directory and with an editor modify/add/delete in the file MakeDisk0QPM.bat the various lines "cpmcp -f z80mbc-d0 %dskfile% CPM-files\xxxxx.yyy 0:xxxxx.yyy" to match the directory in your host (if needed) and all the files to load (xxxxx.yyy);
      2. From the cpmtools directory open the provided DOS command shell and give the following command (I'll use here the name disk0QPM.dsk for the disk image file):
        MAKEDISK0QPM disk0QPM.dsk
      3. After the execution copy the file disk0QPM.dsk in the SRecord directory;
      4. Go to the SRecord directory, open the provided DOS command shell and give the following command:
        D0TOHEXQPM disk0QPM.dsk
      5. After the execution you will find four files named from disk0QPM_SEG0.hex to disk0QPM_SEG4.hex to upload into the virtual disk with iDisk.

      Remember that you...

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  • A new OS: QP/M 2.71 and a RTC for timestamping

    Just4Fun05/23/2017 at 15:37 0 comments

      Here is an interesting alternative to CP/M developed by MICROCode Consulting that supports also file timestamping, and it is 100% CP/M 2.2 "compatible".
      MICROCode Consulting has released the original installation files and all the documentation in their site with the "restricted usage" condition, that means free for non-commercial use and for personal use only, so it should be ok for us. Anyway I've sent them a mail about this project.
      To enable timestamping you need a DS3231 based RTC module like this one:


      WARNING: these modules can cause battery "explosion"! How to fix it

      This cheap modules have a trickle charging circuit that may cause the "explosion" of the battery if you use a standard CR2032 cell. More, it can damage also a rechargeable LIR2032 cell (see this thread). So the safer thing is "disable" the trickle charging circuit (a CR2032 can last 5/10 years, so there is no practical need to a rechargeable battery, after all...).
      To avoid any charging current flowing into the battery you can take away the series limiting 200 Ohm resistor (or cut the trace). Alternatively you can take away the red diode, or destroy it (it is in series with the 200 Ohm resistor). In the following photo you can see the module with some Kapton tape (used as thermal barrier) before to desolder the 200 Ohm resistor (on the right marked as 201) with an hot air gun:

      And here after the desoldering:

      Now the module it's safe and a CR2032 can be used. To connect it use the SCL/SDA/VCC/GND terminals and connect them at the corresponding pins of the IOEXP/I2C connector of the Z80-MBC (pay attention because the position of the signals is different):


      QP/M quick set up guide

      The setup is quite similar to those used to install CP/M. The Assembler automated toolchain must be already set up and the Virtual Disk Module present.


      Here all the steps:

      1. Connect the DS3231 module (with the CR2032 battery inside);
      2. Update the IOS using the new file S221116_R110517_Z80.ino in the File section;
      3. Reboot the Z80-MBC and from a terminal emulator you'll see this:
        Press Y. If you are enough fast you have the RTC set up with the right date/time taken from the sketch compile time (if you are lazy like me you'll find this very handy...). In any case it is possible adjust the date/time manually too from the boot selection menu;
      4. Reboot the Z80-MBC again and select the iLoad boot mode;
      5. From the File section download the file "QPM271_DiskPack.zip", unzip it in the directory used for the Assembler automated toolchain;
      6. Upload the file "iDisk - S250317.hex" to the Z80-MBC using the Dos batch L.BAT (see Assembler automated toolchain) with the command:
        L "iDisk - S250317.hex"
        
      7. When iDisk waits for the input stream, from the Tera Term menu select "File" -> "Send file..." and choice one of the unzipped .hex file from QPM271_DiskPack.zip;
      8. Repeat step 7 for all the four files;
      9. Press the Reset button on the Z80-MBC and enter into the boot selection menu and select 4 to load the OS from disk 0 (and select the disk light ON if not already done, to have an idea of the behavior):

      NOTE: as already noticed, if you experience errors during the serial upload increase the delay after each line from the Tera Term menu (Setup -> Serial port -> Transmit delay -> msec/line). In my VM I set up a 90ms delay. This is due because Arduino serial port doesn't have any handshaking.

      Now you have QP/M 2.71 up and running, but you need further operations to enable the file timestampig (as stated in the QP/M Installation Guide):

      1. To enable file disk timestamping it is necessary run the utility QSTAMPX from A:
        and do the "disk timestamping" for both A: and B: disks.
        When done type the command D $T and check that the output is similar to this:

      2. Now to set up a starting date to all files give the command QSUB SETDATE to run a simple batch that I made to do this initialization easily;
      3. Copy the file SETDATE.QSB to drive B: (using the command QPIP B:=SETDATE.QSB) and repeat from B: the same batch (QSUB SETDATE). Now the command D $T will give this output:...
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  • AUTOEXEC for CP/M

    Just4Fun05/02/2017 at 16:39 1 comment

      Playing with the Z80-MBC I realized that there was a missing feature: to run a program automatically after the "cold" boot.
      So after some searches I found a way to implement in the BIOS a function similar to AUTOEXEC.BAT for DOS using the CP/M SUBMIT command and a batch file that I called AUTOEXEC.SUB (of course...).
      Editing the AUTOEXEC.SUB file it is possible to run a sequence of commands after the cold boot (as with AUTOEXEC.BAT for DOS), and it is possible enable or disable the execution of the AUTOEXEC batch file from the IOS boot selection menu (but this isn't possible with DOS...).


      AUTOEXEC for CP/M quick set up guide

      You must have CP/M 2.2 already up and running (see CP/M 2.2, iDisk and a new IOS), and you can have also only a "single disk" installed (but I recommend the original dual disk configuration), meaning that only U1 (see the A110417 schematic) is populated. Of course the Assembler automated toolchain must be already set up.


      Here all the steps:

      1. Update the IOS using the new file S221116_R300417_Z80.ino in the File section;
      2. Reboot the Z80-MBC and select the iLoad boot mode;
      3. From the File section download the file CPM22SYS_BIOS_S050217_R300417.hex. This file contains only the new CP/M system image for the system tracks of Disk 0, so the "user files" will be left untouched;
      4. Upload the file "iDisk - S250317.hex" to the Z80-MBC using the Dos batch L.BAT (see CP/M 2.2, iDisk and a new IOS) with the command:
        L "iDisk - S250317.hex"
      5. When iDisk waits for the input stream:from the Tera Term menu select "File" -> "Send file..." and choice CPM22SYS_BIOS_S050217_R300417.hex. After the upload iDisk will show a summary, at this point press W to proceed and confirm your choice (as done for the CP/M 2.2 installation described in CP/M 2.2, iDisk and a new IOS). Wait until the write and verify phase is completed.
      6. Press the Reset button on the Z80-MBC and enter into the boot selection menu and select 4 for CP/M loader.


      All done!


      NOTE: as already noticed, if you experience errors during the serial upload increase the delay after each line from the Tera Term menu (Setup -> Serial port -> Transmit delay -> msec/line). In my VM I set up a 90ms delay. This is due because Arduino serial port doesn't have any handshaking.


      How use it

      To create or edit AUTOEXEC.SUB from drive A, you can use the ED command or an other editor like the Turbo Pascal editor. In this case remember to terminate the file with a CR, or "strange" things will occur when executing the SUBMIT AUTOEXEC command.
      You can test the execution giving the command SUBMIT AUTOEXEC from drive A (you can omit the extension .SUB inside the SUBMIT command).
      To enable the AUTOEXEC execution after the cold boot change the corresponding state to ON from the usual IOS boot selection menu.
      If the AUTOEXEC is enabled but the AUTOEXEC.SUB file doesn't exist in the drive A, an error will be displayed:


      New "disk packs"

      I've updated both "disk packs" in the files CPM22_DualDiskPack_v2.zip and CPM22_SingleDiskPack_v2.zip with the new BIOS in the system tracks. So if you are installing them for the first time or you need for any reason to reload them, the new BIOS will be installed. I've added an example of AUTOEXEC.SUB too.


      How it works

      The "trick" used was to inject the string "SUBMIT AUTOEXEC" into the CCP (the Command Processor of CP/M) input buffer. The BIOS after the cold boot checks if the AUTOEXEC flag is set in the IOS, and in this case makes the injection. When the CCP starts after the cold boot, it runs this injected command.

      In this video there is an in depth explanation for a "legacy" Altair 8800 clone.

      The CP/M 2.2 and the new BIOS sources are in the file "CPM22 BIOS - S050217 R300417.zip" in the File section.

  • CP/M 2.2, iDisk and a new IOS

    Just4Fun04/20/2017 at 20:36 1 comment


      CP/M 2.2 quick set up guide

      The set up is very simple. I've done an utility (iDisk) to simplify all the needed operations. Of course the Virtual Disk Module must be present, but you can have also only a "single disk" installed (but I recommend the original dual disk configuration), meaning that only U1 (see the A110417.pdf schematic) is populated.
      The Assembler automated toolchain must be already set up.


      Here all the steps:

      1. Update the IOS using the new file S221116_R130417_Z80.ino in the File section;
      2. Reboot the Z80-MBC and select the iLoad boot mode (if not already selected);
      3. From the File section download the file "iDisk - S250317.hex" and copy it into your PC in the directory used for the Assembler automated toolchain . (Do not use the source file "iDisk - S250317.c" because it requires a special compiling option);
      4. From the File section download the file "CPM22_DualDiskPack.zip" and unzip it (for a single disk configuration download the file "CPM22_SingleDiskPack.zip"). Each disk image is divided into four .hex files called "segment" (32kB each) that are named accordingly (e.g. D0XXX_SEG1.hex means the segment 1 of disk 0);
      5. Upload the file "iDisk - S250317.hex" to the Z80-MBC using the Dos batch L.BAT (see Assembler automated toolchain) with the command:
        L "iDisk - S250317.hex"
        	
      6. When iDisk waits for the input stream:
        from the Tera Term menu select "File" -> "Send file..." and choice one of the unzipped .hex file from CPM22_DualDiskPack.zip (or CPM22_SingleDiskPack.zip for a single disk configuration). After the upload iDisk will show a summary:
        at this point press W to proceed and confirm your choice.
        You don't have to follow any order in the "segments" upload sequence, iDisk will know how to do. To know before each upload what "segments" have been already written into the disks just see the "Disk segment write status":
        in the photo the segments 0, 1 and 3 of Disk 1 have been already successfully written, so you can choose any of the remaining;
      7. Repeat step 6 for all the eight (or four for the single disk pack) "segment" files;
      8. Press the Reset button on the Z80-MBC and enter into the boot selection menu:
        select 4 for the CP/M loader (and select the disk light ON if not already done, to have an idea of the behavior).

      All done!


      NOTE: if you experience errors during the serial upload increase the delay after each line from the Tera Term menu (Setup -> Serial port -> Transmit delay -> msec/line). In my VM I set up a 90ms delay. This is due because Arduino serial port doesn't have any handshaking.


      Disk speed

      The Virtual Disk Module is based on simple EEPROMs using a 200KHz I2C serial bus. Of course do not expect the same speed of an hard disk with a DMA controller!
      The speed probably is like using the floppy drive of those days...


      Single disk configuration

      You can have also only a "single disk" installed (but I recommend the original dual disk configuration), meaning that only U1 (see the A110417.pdf schematic) is populated.

      In this case you have about 120kB free, because the first two tracks of Disk 0 are reserved for the system image (Disk 1 doesn't have the system image, so all the 32 tracks are used for the file system).

      Because the BIOS is the same and is configured for a dual disk system, if you try to select the "B:" drive you'll get a "BAD SECTOR" error.


      Disk pack contents

      In the disk 0 image there are the various external CP/M commands, the Basic interpreter, the CP/M Assembler and the Macro Assembler.
      I've added also D, an alternative DIR command, and PEG, a bin to hex converter (and vice-versa) to exchange files:

      In the disk 1 image there is the complete Turbo Pascal compiler v3.01A with a sample program (SA.PAS):

      In the "single disk pack" the CP/M Assembler and the Macro Assembler are missing, and the Turbo Pascal is without the installing executable (not a big issue anyway) and without the sample program.


      In a next Log I'll explain how create custom disk images.


      Mind the .map!

      During the development of iDisk I encountered "strange"...

    Read more »

  • Virtual Disk Module, a new IOS and ViDiT

    Just4Fun04/13/2017 at 19:37 3 comments

    It's time for a new "module", the Virtual Disk Module! In the photo is that one on the right, near the previous GPIO module.

    In the File section is possible see the simple schematic A110417.pdf with two I2C EEPROM 24LC1025.

    With this module it is possible to emulate two disks of 128kB each (probably like the floppy disk drives of those years).

    Each disk is divided into 32 tracks of 32 sectors. Each sector is 128 bytes long.

    Of course to manage this new HW there is a new release of IOS. The new file S221116_R180217_Z80.ino is in the File section.

    This new IOS checks if the module is present and prints a message if found:

    There is also a new item in the boot selection menu if the virtual disk is found, to use the User led as a disk activity led:

    I suggest to activate this option to have an idea of the behavior.


    ViDiT

    In the File section I've added a simple test program (file "ViDiT - S090417.c") to check the virtual disk. Of course you need to compile it with the C "toolchain":


    About I2C speed

    With this IOS the I2C speed is 200KHz. Note that if you are using a 16MHz external quartz to clock the Atmega32 the I2C speed will be 400kHz. In this case I suggest to lower the two 4k7 pull-up resistors (on SDA and SCL signals) to about 2k2.



    The next Log will bring the CP/M 2.2 up and running...

  • Forth language, new multi-boot selection and a new name

    Just4Fun02/17/2017 at 21:33 4 comments

    Forth


    Thanks to Bill Westfield now we have a new language for the Z80-MBC, the fig-FORTH v1.3 (here the link to the Bill GitHub repository with the source he adapted for the TASM assembler with the needed modifications for the Z80-MBC).

    The acronym "fig" stands for "Forth Interest Group", that was a world-wide non-profit organization (now dissolved) for the promotion of the Forth computer language.
    I've just started to play with this thing, and I must say that it is not the most friendly language I've seen... anyway it is an interesting different approach.

    To enable Forth just upload the new IOS release S221116_R120217_Z80.ino in the Files section, and select the Forth language from the new multi-boot menu (see next paragraph).

    Here it is a "blink" demo program:

    ( ****************************
    (                     
    ( Blink test - Forth - Z80-MBC
    (
    ( ****************************
    : ledon 1 0 P! ;
    : ledoff 0 0 P! ;
    : delay 4000 0 DO NOOP LOOP ;
    : blink CR ." Blinking..." CR BEGIN ledon delay ledoff delay 0 UNTIL ;

    To execute give the command "blink":


    If you are using Tera Term to send a text file to load a forth source, remember to set up a delay of 1ms for each character (serial port managed by the Arduino bootlader doesn't have any handshaking, so for now this is required to handle the serial stream without errors when sending a text file using a terminal emulator):


    New multi-boot selection


    Now pressing the User key after a reset brings to a new menu to chose the preferred boot mode. During this phase the LED-D0 will blink until you choose the boot mode:


    New name


    As you can see from the previous photos, from this release the MBC acronym changes to "Multi Boot Computer"...

  • An automated C language toolchain

    Just4Fun02/09/2017 at 21:26 0 comments

    Here how set up a toolchain to program the Z80-MBC using the C language. It is based on SDCC (Small Device C Compiler) and uses the same "process" of the previous Assembler toolchain.
    In the following it is assumed the the Assembler toolchain is already set up in a Windows host as described in in the Log: New iLoad boot mode and an automated Assembler toolchain.
    So only the SDCC relevant part is explained here.


    Here it is a short video with the toolchain in action:

    What you need to do:

    1. Create a working directory (or use the previous one) where to store the C sources and the two batch files (C.BAT and L.BAT) in the C_batch.zip file from the File section (if you are using the same assembler working directory overwrite the previous L.BAT);
    2. With a text editor search the line:
      "C:\Program Files\teraterm\ttermpro.exe" /c=3 /BAUD=9600 /w="Z80-MBC Terminal" /m=LoadZ80.ttl
      inside C.BAT and L.BAT and verify that both the path and the COM number (/c=3 means COM3) meet your system;
    3. Download and install SDDC from here;
    4. Download the file S030217_crt0.s from the Files section in the working directory;
    5. Open the DOS command line and give the command: "sdasz80 -o S030217_crt0.s".
      Then rename the generated S030217_crt0.rel as crt0.rel. Copy it in the SDCC directory "C:\Program Files\SDCC\lib\z80" (may be a bit different in your system) overwriting the old one.

    All done!

    As usual close Tera Term before every new upload.

    To check if it is all ok, download from the File section the file C_demo.zip and unzip it in the working directory.
    From the DOS command line give the command: "C Blink.c" to check if all the toolchain works as in the video.
    Try also the other demo ANSItest.c (taken from here) to check the ANSI capabilities of a different terminal emulator or a physical terminal:

    About SDCC

    I'm pretty new to SDCC. The SDCC documentation is 8051 "focused", so the given examples can be misleading if used with an other processor in mind.
    When "porting" SDCC to a target HW, there are 3 things to prepare:

    • customize the crt0.rel file that contains the initialization code for the target system;
    • add to the library the function putchar(char c) to send output to the console;
    • add to the library the function getchar() to read from the keyboard.

    I found the documentation quite missing about how to modify for a custom system.
    In particular in the provided crt0.s example there isn't a needed global declaration of three variables (l__INITIALIZER, s__INITIALIZED and s__INITIALIZER). Without this declaration the code will not compile.
    And to make this customization you need to know how the provided assembler works, but the assembler manual is not provided. So you must find it googling...
    If you are used to the Arduino IDE, read carefully the SDCC manual. This C compiler is a lot more "rude" about types and syntax... (as C standard is...).

    Last minute update

    Just found the assembler and linker documentation here!

  • Two layers PCB!

    Just4Fun02/06/2017 at 20:44 0 comments

    Thanks to Bill Westfield now we have a beautiful ready to made PCB!


    I've uploaded in the Files section all the Eagle files (schematic + PCB) zipped as 4chipZ80-Eagle-PCB.zip.
    There are two versions, the first one with some little bugs and a second one with the needed corrections (see the "readme" file inside the zip for the explanations).

    In any case I suggest to check at the Bill GitHub repository here for any update/information before sending it to a service (so you are sure to use the last updated version...).


  • New iLoad boot mode and an automated Assembler toolchain

    Just4Fun01/31/2017 at 20:36 4 comments

      This new IOS release (S221116_R230117_Z80.ino in the Files section) brings a new dual-boot mode. Now it's possible choose if boot with the usual Basic or use the new iLoad boot mode.
      iLoad (S260117.asm in the Files section) is an Intel-Hex bootloader that allows to load from the serial port a binary program using the Intel-Hex format, and execute it. I've used a large part of the source from this site.

      To select a boot mode just push the Z80-MBC Reset button and immediately after push the User button at least until the User led turns off.
      The selection works as a toggle switch, and is stored in the EEPROM.
      Here it is a video that shows how to switch:

      Using the iLoad boot mode it's possible to automate all the process from the source to the execution in the target.
      This video shows an automatic Assembler toolchain; only one command from the source assembler to the execution on the target (the source file BlinkDemo.asm used in the video is in the File section):


      HOW TO SET UP AN "AUTOMATED" ASSEMBLER TOOLCHAIN

      What you need to do:

      1. Set up a Windows host or a VM (Virtual Machine). I've used a Windows XP SP3 VM onto a linux host;
      2. Load the Windows driver for your serial-USB adapter. Remember that your dongle *must* have the DTR signal;
      3. Create a working directory where to store the assembler sources, the assembler program and the two batch files (A.BAT and L.BAT) in the asmbatch.zip file (see the File section). With a text editor search the line:
        "C:\Program Files\teraterm\ttermpro.exe" /c=3 /BAUD=9600 /w="Z80-MBC Terminal" /m=LoadZ80.ttl
        inside A.BAT and L.BAT and verify that both the path and the COM number (/c=3 means COM3) meet your system;
      4. Download and copy in the previous directory the TASM v3.2 assembler from here. The on-line manual is here;
      5. Download and install the "Tera Term" terminal emulation from here;
      6. Set up Tera Term. From the Tera Term "Setup" menu select "Serial port..." and configure the parameters for your COM<n> connection to your serial-USB adapter. Set 9600 Baud, 8N1, Flow control none, Transmit delay 40ms/line. Save configuration with "Save setup..." from the "Setup" menu;
      7. Copy the file LoadZ80.ttl (see Files section) in the "Tera Term" installation directory, where it is installed the main file ttermpro.exe (for a standard installation for an English Windows version should be "C:\Program Files\teraterm");
      8. Open the file LoadZ80.ttl with a text editor and go to line 10. Edit the "setdir" parameter to meet your working directory path and name created at point 3. on your system, and save the file;
      9. Open the DOS command line and go in the working directory (using the CD dos command), attach the serial-USB dongle to the Z80-MBC and for a VM "connect" the dongle to the emulated usb of your VM. All done!

      Now it's time to check if it is all ok. From the DOS command line give the command: "A blinkdemo.asm" to check if all the toolchain works as in the video. To load the last compiled program give the command "L" without parameters. To load a specific intel-hex file give the command "L <filename.hex>".

      Close Tera Term before every new upload.


      iLoad behavior

      Please remember that iLoad will take the first address of the intel-hex stream as the starting address of the program, and after the loading will jump to it.
      iLoad will check the hex stream for errors, and protects itself if "someone" try to load a program (or a part) over it ("illegal address" error).

  • GPIO Expansion Module

    Just4Fun01/22/2017 at 13:50 2 comments

    This is the first add-on module for the Z80-MBC. It is a 16x GPIOs expansion module based on a MCP23017 IC, and can be easily connected to the Z80-MBC using the IOEXP connector (based on a I2C serial interface), of course on a breadboard...

    In the Files section I've added the schematic (A080117.pdf) and all the KiCad4 files (A080117 Kicad4.zip).
    There is also a new release of the IOS (S221116_R200117_Z80.ino) that takes care of it. During the boot phase, if the GPIO expansion module is found, a specific text is displayed:

    No configuration is needed, just plug it.

    Here is a short demo video:


    Each GPIO can be configured as input or output, and for each single input it is possible activate a 100K pull-up resistor. Of course this can be done from the Basic language, using new "virtual" I/O addresses as a language extension (if the module is not present, these I/O addresses are simply ignored):

    New WRITE I/O addresses:

            0x03:
              // GPIOA write (GPIO Expansion Module):
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    GPIOA value (see MCP32017 datasheet)
                      
            0x04:
              // GPIOB write (GPIO Expansion Module):    
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    GPIOB value (see MCP32017 datasheet)
              
            0x05:
              // IODIRA write (GPIO Expansion Module):
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    IODIRA value (see MCP32017 datasheet)
                      
            0x06:
              // IODIRB write (GPIO Expansion Module):
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    IODIRB value (see MCP32017 datasheet)
                      
            0x07:
              // GPPUA write (GPIO Expansion Module):
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    GPPUA value (see MCP32017 datasheet)
                     
            0x08:
              // GPPUB write (GPIO Exp. Mod. ):
              //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
              //                            ---------------------------------------------------------
              //                             D7 D6 D5 D4 D3 D2 D1 D0    GPPUB value (see MCP32017 datasheet)

    New READ I/O addresses:

              0x03:
                // GPIOA read (GPIO Expansion Module):
                //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
                //                            ---------------------------------------------------------
                //                             D7 D6 D5 D4 D3 D2 D1 D0    GPIOA value (see MCP32017 datasheet)
                //
                // NOTE: a value 0x00 is forced if the GPIO Expansion Module is not present
               
              0x04:
                // GPIOB read (GPIO Expansion Module):
                //                I/O DATA:    D7 D6 D5 D4 D3 D2 D1 D0
                //                            ---------------------------------------------------------
                //                             D7 D6 D5 D4 D3 D2 D1 D0    GPIOB value (see MCP32017 datasheet)
                //
                // NOTE: a value 0x00 is forced if the GPIO Expansion Module is not present

    And here is the Basic program used in the video (the HW wiring is shown in the comments):

    1 REM * * * GPIO EXPANSION MODULE (A080117) DEMO  * * *
    2 REM
    3 REM (USER Key -> slow led, GPIO-A(9) Key -> fast led)
    4 REM --------------------------------------------------
    5 REM Demo HW wiring (see A080117 schematic):
    6 REM
    7 REM   GPIO-B
    8 REM    (J3)
    9 REM   +----+   LED
    10 REM  | 2  |--->|---+
    11 REM  | 3  |--->|---+      RESISTOR
    12 REM  | 4  |--->|---+        680
    13 REM  | 5  |--->|---+-------/\/\/-----o GND
    14 REM  | 6  |--->|---+
    15 REM  | 7  |--->|---+
    16 REM  | 8  |--->|---+
    17 REM  | 9  |--->|---+
    18 REM  +----+        |
    19 REM                |
    20 REM                |
    21 REM  GPIO-A        |
    22 REM   (J4)         |
    23 REM  +----+   LED  |
    24 REM  | 2  |--->|---+
    25 REM  | 3  |--->|---+
    26 REM  | 4  |x 
    27 REM  | 5  |x
    28 REM  | 6  |x
    29 REM  | 7  |x     PUSH BUTTON            RESISTOR
    30 REM  | 8  |x        ---                   1K
    31 REM  | 9  |---------o o------------------/\/\/-----o GND
    32 REM  +----+ 
    33 REM
    34 REM
    35 REM
    36 REM --------------------------------------------------
    37 REM
    38 REM Set MCP23017 GPIOB all pins as output (IODIRB=0x00)
    39 OUT 6, 0
    40 REM Set MCP23017 GPIOA 0-1 as output, others as input (IODIRA=0xFC)
    41 OUT 5, 252 
    42 REM Set MCP23017 GPIOA 2-7 pull-up resistor on (GPPUA=0xFC)
    43 OUT...
    Read more »

View all 11 project logs

  • 1
    Quick instructions intro:

    All the detailed instructions are provided in the "DETAILS" section and in every "LOG".

    Because this project has grown a lot on the way (more than I've supposed at the beginning...) here you can find a short and simple build guide without "navigate" into all the various "LOGs".

    This short guide is referred to the current (at present date 31 August 2017) last "level" of development as described in "A new OS: QP/M 2.71 and a RTC for timestamping".

  • 2
    Add the Atmega32 support in your Arduino IDE:

    The standard distribution of Arduino IDE doesn't have the Atmega32 "core" support files.

    You need to add them from here.

  • 3
    Flash the Atmega32:

    First of all you need to flash the Arduino bootloader into the Atmega32.

    To do this there are a lot of ways. I use a cheap USBASP programmer that you can find "around" for less than 2$.

    Remember to select from Arduino IDE the "Atmega32 8MHz Internal" clock option before flashing the bootloader!!!

View all 6 instructions

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Discussions

WestfW wrote 5 days ago point

New commit for the PCBs at https://github.com/WestfW/4chipZ80


Add VCC/GND labels to bottom silk for new prototype-area vias.Bump version to V2.1 to account for the new power vias in prototype area.
rename files to reflect version number (Z80-4chip-v2.1.*)
Add zip of v2.1 gerbers to Gerbers-V2 directory.

(also fixes the r16/r17 "problem.")

@Cyril V. says he's built and tested a V2 PCB; since V2.1 changes are so minor, it should work as well.  I've got a tentative V3 that adds the I2C memory, but I'm hesitant to make that level of change when the chances of someone actually building or testing them is so small.  Unfortunately (?), a "working" V1 with things added to the proto area is "good enough" for my uses.

  Are you sure? yes | no

Just4Fun wrote 5 days ago point

Great!

BTW: these days I'm just started a new FPGA project... It should be "Grant's Multicomp" compatible, so it should "run" a complete VHDL Z80, 6800, 6809, 6502 system with VGA and Keyboard... Hmmm, long way... may be this time I'll see the Magic Smoke go away.... :-)

  Are you sure? yes | no

Cyril V. wrote 4 days ago point

Thank you for you work West. If you post it (V3) I will order a batch.

  Are you sure? yes | no

john wrote 4 days ago point

Cyril - I’ll kick in a little $ for a couple of boards from that batch...

  Are you sure? yes | no

Greg Walker wrote 11/04/2017 at 11:49 point

Interesting concept. I like the idea of utilising the ATmega MCU as a bootloader and to transfer the OS to RAM. I note the pull down resistors R5-R12 on address lines A9-A15. As the Mega is limited to the first 1K of address space I'm not sure how you're loading above that memory space. I understand why you'd put them there to prevent the inputs floating.

Think I'll have to have a good read through the ATMega code to work out how you're uploading beyond the first 1K.

Good work on this! I think I've found my next project.

  Are you sure? yes | no

Just4Fun wrote 11/05/2017 at 21:24 point

Thanks! You can find some info about the boot process here:

SOFTWARE INTERNALS: The boot process

  Are you sure? yes | no

Peabody1929 wrote 11/02/2017 at 17:15 point

Instead of adding an EEPROM with an I2C interface, why not build an I2C interface for a Flash EPROM?  It could be as simple as a pair of MSP23017SP and a 29F040.  This would give I2C R/W access to a 512KB flash disc.   

  Are you sure? yes | no

Just4Fun wrote 11/05/2017 at 21:44 point

The next Z80-MBC-2 very likely will use a SD disk, so probably no more eeprom...

I've "planned" the development of the new Z80-MBC-2 after the completion of a new FPGA project I've just started now...

  Are you sure? yes | no

siffland wrote 11/01/2017 at 02:37 point

How hard would it be to add a 24LC256 as a third 256k disk (i think cp/m can address 256k.)


Also has anyone gotten xmodem or zmodem to work, i got kirmet on there (custom disk image), but cannot get it to transfer files across the serial port.

Sorry just playing around, always want it to do more.  OK i just want to play zork.

  Are you sure? yes | no

Just4Fun wrote 11/01/2017 at 08:42 point

Hi, about the 24LC256... it is a 256Kbit EEPROM so... it is 32K x 8bit = 32KB (B=bytes).... I don't think that it would be so useful... :-)

  Are you sure? yes | no

siffland wrote 11/01/2017 at 23:52 point

Your right, just trying to get more space.  I didn't read the spec sheet. 

Would adding more disks be as easy as defining more EXT_EEPROM?'s and giving them new addresses?  Formatting them might be problematic, but i can probably figure that out.

  Are you sure? yes | no

Just4Fun wrote 11/05/2017 at 21:31 point

You need to modify the BIOS too, as stated in the "CP/M Alteration Guide"...

And modify some code in the Virtual Disk "engine", inside the sketch...

And modify iDisk...

And probably other things...

  Are you sure? yes | no

villaromba wrote 10/22/2017 at 13:22 point

Yes, well done indeed!! I have learnt a lot  successfully constructing this project all the way through with all the add-ons.  The software side (not my main strength) has also taught me a lot and given me a much broader understanding.  I do hope that further developments can take place but fully aware that  these  don't happen overnight !!! 

  Are you sure? yes | no

Just4Fun wrote 10/22/2017 at 16:10 point

Thanks you! I'm currently "playing" with some CPLD/FPGA stuff (as you can see), but I've a lot of improvements for this project too. Of course they will require deep changes a lot of time...

  Are you sure? yes | no

WestfW wrote 10/22/2017 at 00:28 point

Congratulations!
https://hackaday.com/2017/10/21/these-twenty-projects-won-1000-in-the-hackaday-prize/#more-277969

(There are two things that particularly impress me with this project:

1) The number of people that have actually constructed it (and in several different ways.)

2) the amount of additional work that has gone into improving the project.

These are really significant accomplishments, in a world where so few "things" ever get much past the original version by the original designer.)


  Are you sure? yes | no

Just4Fun wrote 10/22/2017 at 16:04 point

Bill, thanks you a lot for yours beautiful words!

  Are you sure? yes | no

john wrote 10/23/2017 at 14:06 point

Totally agree - aside from this being fun from the retro-computing angle, having built it, debugged my sloppy wiring and modifying the code for my specific changes was a great way to learn and was time well spent!

  Are you sure? yes | no

Just4Fun wrote 10/26/2017 at 19:59 point

  Are you sure? yes | no

joel076 wrote 10/16/2017 at 18:13 point

When i try to upload hex files it doesnt display the data, what could i be doing wrong?

  Are you sure? yes | no

Just4Fun wrote 10/20/2017 at 09:06 point

Hi, could you add more details...?

  Are you sure? yes | no

joel076 wrote 10/28/2017 at 10:41 point

The computer is working and it displays the choices but when i try to upload a hex file the macro just stops at line 40 and doesnt display any data.

  Are you sure? yes | no

WestfW wrote 09/11/2017 at 09:58 point

Sigh.  I keep going down this path:

1) gee, it should have a front panel!  To monitor the address and data buses, you know.

2) Binary or Hex?   Hex, I guess; I've got all those 4-digit displays.

3) So you need a binary-to-7seg (hex) decoder, eh?

4) Sure!  I'll use a micrcontroller.  I can get 4digits (multiplexed) worth out of a $2 micro; cheaper than 7447s were, back in the day...

5) 24bits (16 address, 8 data) worth, though?  Ok - another ATmega32!  Or two.  Maybe an m328 to read the bits and an m8 to drive the displays?

6)  ANOTHER couple of AVRs?  You've now got more memory in the support micros than in the Z80 system...  (depressed.)

(What about switches?!)

  Are you sure? yes | no

Just4Fun wrote 09/11/2017 at 12:36 point

LOL...  Are you thinking about an Altair like front panel...? :-)

May be something like this... https://hackaday.io/project/20011-altair-8800-front-panel-ardiuno-shield

  Are you sure? yes | no

WestfW wrote 09/14/2017 at 08:42 point

I think I have something like the KIM-1 readout in mind, or maybe a COSMIC ELF (though that used expensive internally decoded dot matrix displays, and only two of them, IIRC.)
I keep wandering off into thoughts of  HCMS29xx, OLED, and LCD displays, too.  NO!  I bought that big box of clock LED displays and I WILL USE THEM!

  Are you sure? yes | no

Dutchman wrote 08/28/2017 at 01:52 point

Hi, i have a question about the Z80, i couldn't find your z80 (Z84C004) and could only find the Z84C0020, and from what i understood the only difference between these two is the speed at wich they need to run (your z80 at 4Mhz and mine at 20Mhz), since im quinda of noob could you explain what are the alterations to be made to the board in order for these to work ?

  Are you sure? yes | no

Just4Fun wrote 08/29/2017 at 06:20 point

Hi, you can use the Z84C0020 without any change. The minimum clock frequency for *any* CMOS Z80 is 0Hz (DC)!

  Are you sure? yes | no

WestfW wrote 08/09/2017 at 21:30 point

Can you attach a "license" of some kind to the design and various firmware bits?
I had someone asking about the PCB license (now explicitly CC BY-SA 4.0, unless that's unacceptable to you.)  Various institutions and distribution mechanisms get pretty fussy about having an explicit license that their lawyers can understand.

  Are you sure? yes | no

Just4Fun wrote 08/10/2017 at 06:33 point

Hi, I'm completely a noob about "licensing"... :)

So you mean that is better to add an explicit  disclaimer on "every" schematic and SW source file....?

I've added in the bottom of the "Details" a last "paragraph" about licensing. Do you thing that it is enough?

I've added also a licensing note in my git repository (https://github.com/SuperFabius/Z80-MBC). I've "choose" GPL v3 but I haven't no idea if CC BY-SA 4.0 could be "better".

This things drive me crazy....

Could give me some guidance....?


BTW (after some googling...): in the creative common site they say that the CC license is not appropriate for SW/HW....  (https://creativecommons.org/faq/#Can_I_apply_a_Creative_Commons_license_to_software.3F), but here (https://www.fsf.org/blogs/licensing/cc-by-4-0-and-cc-by-sa-4-0-added-to-our-list-of-free-licenses) they say that are "compatible" with GPL v3...  OMG!!!

An other interesting article about HW: https://forum.kicad.info/t/using-the-l-gpl-as-an-open-source-hardware-license/1925/2

  Are you sure? yes | no

WestfW wrote 08/11/2017 at 07:55 point

Grr.  Long reply deleted by the Hackaday.io software...
Interesting links:

http://www.ladyada.net/library/openhardware/license.html

https://www.oshwa.org/faq/

Personally, I'm not fond of "viral licenses" like GPL that insist that everything that comes near them also become open source, and prefer MIT for software.  Other people think that the viral property is really important.

Hardware seems to be problematic because OSSW licenses are based on copyright, but copyright only protects a particual expression of intellectual property.  In theory, when I re-write your pdf schematic in EAGLE and make a PCB, that's a different enough expression that it wouldn't violate the original copyright.

One thing that I think is particularly important is some sort of "statement of intent" - just write what you want to allow and disallow, in plain english rather than license-eese.  It may not hold up in court, but at least people will have a good idea whether they're intentionally going against your wishes or not.  For example, you can find Arduino statements to the effect that they intend to allow commercial and proprietary products to be based on the Arduino core (and hardware), which is comforting in spite of the fact that some of the licenses they use are pretty ambiguous when it comes to embedded firmware...

  Are you sure? yes | no

Just4Fun wrote 08/11/2017 at 10:57 point

To keep it simple, now there is a "Licensing" paragraph at the end of the main "Description/Details" paragraph, and on the git repository the "LICENSE" file too (as you did in your repository). All GPL v3, that should be compatible with CC BY-SA 4.0.

I've added a "fair" request to mention the author if someone uses this material... :)

I think that now it should be sufficient (isn't it...?).

  Are you sure? yes | no

k8lh wrote 07/27/2017 at 23:27 point

Very nice project. 

Can an ATMEGA1284P be used instead of the ATMEGA32A?  If so, are any changes required in the Arduino sketch?

Cheerful regards, Mike

  Are you sure? yes | no

mick wrote 07/28/2017 at 19:13 point

They look very similar to me, apart from the increased memory spaces on the 1284P. Pinouts & operating voltages seem to be the same.  I should think that it would be ok. The Mightycore boot loader supports that chip too. If you've already got one it would definitely be worth a try.

  Are you sure? yes | no

Just4Fun wrote 07/29/2017 at 19:54 point

Hi, yes it is  possible.

An other user (Steve) has successfully used an Atmega644 that it is quite similar to yours (search among the comments). He changed the clock activation code. This is necessary because Atmega644/1284 have some differences in some register naming.

Here the modification he did:

// Initialize CLK @ 4MHz. Z80 clock_freq = (Atmega_clock) / (OCR2 + 1) = (Atmega_clock) / 2
  ASSR &= ~(1 << AS2);
  TCCR2B |= (1 << CS20);
  TCCR2B &= ~((1 << CS21) | (1 << CS22));
  TCCR2A |= (1 << WGM21);
  TCCR2A &= ~(1 << WGM20);
  TCCR2A |= (1 <<  COM2A0);
  TCCR2A &= ~(1 << COM2A1);
  OCR2A = 0;   pinMode(CLK, OUTPUT);

May be that this works in yours case too without others variatons

Let me know...

  Are you sure? yes | no

mick wrote 07/25/2017 at 18:30 point
I think it's one of those things - people find time to play with it when they can. :) That's my position at the moment. Too much stuff all happening at the same time. However, I've also been doing a bit of work on porting Nas-Sys 3 over to make this system look very much like a Nascom 2 running through a tty. Probably not a lot of interest in that (other than for myself!). Is anyone still interested in having somewhere to act as a repository for custom disk images for this project? They aren't very big and I still have quite a bit of spare space on my web site where I could perhaps host them as zip files.

  Are you sure? yes | no

villaromba wrote 07/25/2017 at 14:54 point

Are we at the end of the line on this project or is there more in the pipe-line to come???

  Are you sure? yes | no

Just4Fun wrote 07/26/2017 at 07:22 point

Hi, next items in my "to do" list are an SD card and CP/M 3 with banked RAM. Of course they require an HW/SW update and a lot of time... May be after summer...

Currently I'm playing with an other project (probably I'll publish it here when done)...



  Are you sure? yes | no

villaromba wrote 07/27/2017 at 20:28 point

Awesome!!! I look forward to the Z80 enhancements and 'CPLD Fun Board"!!! But of course enjoy the summer hols first :).

  Are you sure? yes | no

mick wrote 07/03/2017 at 18:57 point
My new baby :) https://www.dropbox.com/s/mbuumplvvw16brc/front.jpg?dl=0
and its backside: https://www.dropbox.com/s/990az27og0slrqz/back.jpg?dl=0
I knew I'd eventually find a use for that wiring pencil...

  Are you sure? yes | no

john wrote 07/03/2017 at 22:46 point

Very nice!

  Are you sure? yes | no

Just4Fun wrote 07/04/2017 at 06:11 point

Neat! I've some wire like yours but never used it...

  Are you sure? yes | no

Dylan Brophy wrote 07/04/2017 at 14:52 point

:-) Z80 computers rule!

  Are you sure? yes | no

Starhawk wrote 07/27/2017 at 22:59 point

What are the chips on that board, if I may ask...?

  Are you sure? yes | no

mick wrote 07/28/2017 at 19:28 point

I mostly used the same chips as the original apart from the RAM chip. I couldn't get that part at a reasonable price, but I could get the 6C1008, which is perfectly fine and pin compatible.

Oh, I also got a faster Z80 as the price difference was very little. My RTC chip is different too.                                                                                                                                                                                                                                                                                                                                                          

  Are you sure? yes | no

mick wrote 07/01/2017 at 16:38 point

I've just got this built using a similar layout to the one that John used, on pad board. I've included the I/O expansion, virtual disks & a DS1307 rtc chip (because I already had one) c/w cell holder lifted from an old motherboard. Still a bit of space left. :)  I'm just considering using it to boot a modified Nas-Sys as a machine code monitor. Possibly even with a crude method of saving & loading to "disk".

I'm no expert, but as only A0-A5 are needed for the loader, couldn't that free 3 AVR pins for use as a SPI interface to a SD card "hard disk"?

  Are you sure? yes | no

Just4Fun wrote 07/03/2017 at 13:14 point

Yes, it can be done... (it is one of the items in my long "to do" list...). Of course you must do the needed modifications in the sketch, and add pull-down resistors on the A6-A8 address lines.

  Are you sure? yes | no

Cyril V. wrote 06/23/2017 at 18:09 point

I just finish building this project - Works at the first boot love it :)  (BTW - I did find here is some Basic games: http://www.moorecad.com/classicbasic/index.html).
 
My goal now is to free some pins on the Atmega32 for some
I/O (VGA/SD...).  After some research, I find this project http://www.shaels.net/uploads/Media/SiteDownloads/Mini80/Mini80b.pdf which use a 74HC165 for the address bus to save 6 pins on the MCU (Propeller).

But the 74HC165 can use access only 8 lines of the address bus vs the 9 lines direct on the Atmega32.

Can I use a 16 bits shift register (with only using 9 lines) like this one  http://users.ece.utexas.edu/~valvano/Datasheets/74F676.pdf and for the code does something like that https://forum.arduino.cc/index.php?topic=50633.0
will work?

(btw - I have couple PCB V2 left than I can sell for $4 + shipping - PM me if interested).

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Just4Fun wrote 06/23/2017 at 19:46 point

Great! :)

BTW: if you want try some modifications, take in account that there are parts of the code that are strictly tied to the Z80 bus behavior...

PS: the 9th address line is not currently used... :) (and the 74F676 seems to be parallel in serial out, so no good anyway)

PPS: So the 24LC512 based virtual disk worked....

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Cyril V. wrote 06/24/2017 at 01:25 point

Thank you for info. I just order couple 74HC165 I will give it a try.

For the 24LC512, I finally manage to find two 24LC1025 for $6 couple the day after on eBay, so I did not bother with the 24LC512. But you can easily find 24LC512 for under $1. 

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Just4Fun wrote 06/24/2017 at 07:07 point

Just checked now... the HC165 are parallel in serial out too, so no good!! (always check the datasheet before buy...).

BTW: take in account that address lines are used for the I/O emulation too...

PS: I've looked at the schematic you linked again... it seems to me a bit "convoluted"... the HC165 is used to READ A0-A7 but the propeller chip has 8 pins not used... very strange...

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Cyril V. wrote 06/25/2017 at 00:11 point

Here is the the website: http://www.shaels.net/index.php/mini80/mini80-general/119-mini8o-overview.

You completely right. Well live and learn :).

The rest of the propeller ports are used for VGA and keyboard:  http://www.shaels.net/index.php/mini80/documents/120-min80-proto1-io-prts-and-devices

The thing is running @ 3.3V : "The CMOS construction of the Z80 should allow the Z80 to operate at a reduced voltage. Digital CMOS devices generally set there logic voltage levels as a percentage of the power supply voltage and not by absolute voltages. This feature should allow the Z80 to operate at the 3.3 volt
level allowing it to interconnect with the Parallax Propeller chip. At
 3.3 volts the Z80 max CPU clock speed will have to be de-rated."

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Just4Fun wrote 06/25/2017 at 13:06 point

Hmmm... the Z80 there is completely out of specs.... No...  this isn't my way... definitely... :)

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villaromba wrote 05/27/2017 at 14:11 point

Finally QP/M up & running - thankyou ! Looking forward to seeing how to add more progs BUT Drive A is R/W, with 24k space remaining. Drive B is R/W, with 42k space remaining.

Where's it all going to go !!!! ???

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Just4Fun wrote 05/27/2017 at 17:30 point

You should use it as a dual floppy machine of those years... I mean using A: for the system and B: for user programs. Of course loading with iDisk the needed disk image, or following the way used by john.

If you do not need turbo pascal just... delete it... :)

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villaromba wrote 06/01/2017 at 20:37 point

Thanks for clear instructions, I need them  :) , ..on how to add  custom images with CP/M Tools. Experimented with B: and it works perfectly with my added programs. 

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john wrote 05/25/2017 at 12:23 point

I could have sworn I read this in the posts somewhere, but I can't find it now.  Can someone tell me how to transfer files to the drive through the console?  I'm wanting to put Zork on the B: drive.  Will PIP do this?

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Just4Fun wrote 05/25/2017 at 14:37 point

For now he only way is convert a file to IntelHex format and send it using the terminal emulation. I think that PIP can be used. See here: http://www.gaby.de/cpm/manuals/archive/cpm22htm/ch1.htm#Section_1.6.4 

You can also use PEG to convert inside the target (Z80).

Anyway you have remembered to me that I have to write a "Log" to describe how create custom disk images... For "large" programs/applications this is the way to go...

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john wrote 05/25/2017 at 17:34 point

That's where i was headed, but I can't get QPIP to do anything with CON: as the source.  I'm putting CP/M back to try that version of PIP (not sure if it's different).

Edit: 

CP/M PIP does seem to work and I can get the file to disk, but because of the bin to hex conversion the file is now too big to fit on the disk.  Looking forward to your next log :)

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Just4Fun wrote 05/25/2017 at 17:44 point

Yep, I was  just trying that... It seems looping...

I've tested on an emulator with standard CP/M and I was able to write a text from the console using PIP, giving also CTRL-J after every CR.

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john wrote 05/26/2017 at 00:59 point

I went around the world to get there, but I eventually got this to work...  I was able to use Grant Searle's DOWNLOAD. COM code from his CP/M project to get the files over.  If anyone's interested, I had to change the DOWNLOAD2.HEX to relocate 0x4100 to 0x0100 and then recalculate the checksums.  Then I pasted that into ZDE and saved it to the disk.  A quick PEG to convert from Intel HEX to a COM file and then just followed the directions to transfer the Zork files over.  Then I found myself "West of House".    :)

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Just4Fun wrote 05/26/2017 at 07:26 point

Great idea!

BTW: I've just ordered "some" HD64180 (=Z180) and MC68008. Starting to think what to do with these... May be next winter mini system... :)

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john wrote 05/24/2017 at 15:06 point

Nice work!  Waiting on the RTC module to arrive, but since I had a spare Arduino I tried the "DS1307 Emulator Library"...  Works great!

Z80-MBC (Multi Boot Computer) - A041116
IOS - I/O Subsystem - S221116 R110517

IOS: Found RTC DS3231 Generic Module (24/05/17 11:00:36)
IOS: Found Virtual Disk Module
IOS: Disk light is ON
IOS: AUTOEXEC execution is OFF
IOS: Loading phase 1 boot program...
IOS: Loading phase 1 done.
IOS: Z80 is running from now.

Z80-MBC CP/M 2.2 Cold Loader - S150417

Loading... done

Z80-MBC QP/M 2.71 BIOS - S080517

QP/M 2.71 Copyright 1985 (c) by MICROCode Consulting

A>time
24-May-17       11:00:43
A>

And from MBASIC:

LIST
10 SECONDS = INP(7)
20 SECONDS = INP(8)
30 MINUTES = INP(8)
40 HOURS = INP(8)
50 DAY = INP(8)
60 MONTH = INP(8)
70 YEAR = INP(8)
100 PRINT "THE TIME IS: ";
110 PRINT HOURS; : PRINT ":"; : PRINT MINUTES; : PRINT ":"; : PRINT SECONDS
Ok


RUN
THE TIME IS:  12 : 36 : 18 
Ok

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Just4Fun wrote 05/24/2017 at 17:05 point

Great! These RTC have the same I2C address and the same structure for the main date/time registers. Instead the "control register" are different and at different location. Anyway it seems that are "compatible" at least in the way I've used it...!

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john wrote 05/24/2017 at 17:14 point

Yes - I think the 3231 control register ends up being in the RAM on the 1307, so writes to it have no effect, and the initial read to check if the OSC is running fails, so the time setting routine gets triggered.  I added a write to the 1307 register to change the SQW pin to 1 Hz and it worked on the emulator.  I found a 1307 in my parts bin, so I'll wire that up soon.

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villaromba wrote 05/27/2017 at 15:53 point

John, thanks for this  info. Where did you find the INP(x) address data from. The module has a temp sensor on it as well, so is it possible to INP that as well ?

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WestfW wrote 05/24/2017 at 05:23 point

Neat!  (Man, I had totally forgotten just how tiny CP/M is...)

----------------------------

IOS: Z80 is running from now.

Z80-MBC CP/M 2.2 Cold Loader - S150417
Loading... done

Z80-MBC CP/M 2.2 BIOS - S050217 R300417
CP/M 2.2 Copyright 1979 (c) by Digital Research

A>dir
A: ASM      COM : D        COM : DDT      COM : DUMP     COM
A: ED       COM : HELLO    COM : LOAD     COM : MAC      COM
A: MBASIC   COM : PEG      COM : PIP      COM : STAT     COM
A: SUBMIT   COM : XSUB     COM : HELLO    ASM : GPIO     BAS
A: AUTOEXEC SUB : HELLO    PRN : HELLO    HEX
A>mbasic
BASIC-80 Rev. 5.21
[CP/M Version]
Copyright 1977, 78, 79, 80 (C) by Microsoft
Created: 15-Dec-80
34811 Bytes free
Ok
10 print 124
list
10 PRINT 124
Ok
run
 124
Ok

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Just4Fun wrote 05/24/2017 at 07:30 point

Now you are ready for QP/M too... :)

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