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Software for Bill Shen's Z280RC Single Board Z280 system on a RC2014 board

This repository contains a snapshot of the original software, plusenhancements, updates and new utilities for Bill Shen'sZ280RC single board Z280 system - as described on the RetroBrew builderswiki at

https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:z280rc

The original software is located in zip files in the "original" subdirectory.

My modifications to Bill Shen's original non-banked CBIOS3 for CP/M 3 arein the "system/cpm3-nonbanked" subdirectory - adding DS1302 clock support.

I've also developed

• A modified CP/M 2 (in system/cpm22) to support file partitions containingup to 2048 directory entries (four 8Mb drives on CompactFlash with 1.5Mb RAMdisk);

• A CP/M 3 BIOS (in system/bios280) supporting Banked memory (up to eightbanks of memory, four (and optionally eight) 8Mb drives, 1.5Mb RAMdisk,optional 4-port QuadSer module);

• Ported UZI280 (in system/uzi280*) - a version of the Unix operating system; and

• Some new utility programs in the "utilities" subdirectory - XMODEM,RESET, TIME, DU, NULU, RELHEX and updated for CP/M 3 versions of DEVICE,HELP and KERMIT.

Minor tweak to XMODEM to look for its configuration file on thesystem drive (in A:XMZ280RC.CFG). Be sure to set this with theSYS attribute so it is seen from all user areas under CP/M 3.

A>set xmz280rc.cfg [sys ro]

Ported the Z280 UART console I/O routines to the latest version ofMartin Eberhard's XMODEM version 2.9. The new version is in the"utilities" subdirectory as a ZIP fileutilities/xm29z280.zipor you can download the individual filesutilities/XM29Z280.MAC,utilities/XM29Z280.HEX andutilities/XM29Z280.COM. This version uses the same configuration fileutilities/XMZ280RC.CFGas the previous version (see below)to obtain its default switch values (/X3 uses the built-in Z280 console UART).

A new utility program to reset the system from CP/M back to theZZmon command prompt. (This is the software equivalent of pressingthe reset button).

Assembler source is inutilities/RESET.MACand a pre-built binary is inutilities/RESET.COM

The CP/M 3 BIOS checks for the presence of a QuadSer module. Ifnone is found then it reports

%QUADSER I/O board not detected

during the system start-up, and it disables the TTY0 to TTY3 devices.

However, the default character device assignments for boththe AUXIN and AUXOUT devices were not adjusted (causing an errorif you tried to use the DEVICE command).

To fix this, I've changed the defaults for the AUXIN and AUXOUTto the NULL device. This means if you have a QuadSer module,then you will now need to use the DEVICE command (in the PROFILE.SUBstart-up file) to configure the AUXIN and AUXOUT devices under CP/M 3.For example -

C>device aux:=tty2[19200,xon]                                                  A:DEVICE   COM  (User 0)                                                                                                                                        Physical Devices:                                                               I=Input,O=Output,S=Serial,X=Xon-Xoff                                            UART   NONE  IOS    TTY0   19200 IOS    TTY1   19200 IOS                        TTY2   19200 IOSX   TTY3   19200 IOS                                                                                                                            Current Assignments:                                                            CONIN:  = UART                                                                  CONOUT: = UART                                                                  AUXIN:  = TTY2                                                                  AUXOUT: = TTY2                                                                  LST:    = Null Device                                                                                                                                                                                                                           C>

To set them back to NULL, use

C>device auxin:=null, auxout:=null                                             A:DEVICE   COM  (User 0)                                                                                                                                        Physical Devices:                                                               I=Input,O=Output,S=Serial,X=Xon-Xoff                                            UART   NONE  IOS    TTY0   19200 IOS    TTY1   19200 IOS                        TTY2   19200 IOSX   TTY3   19200 IOS                                                                                                                            Current Assignments:                                                            CONIN:  = UART                                                                  CONOUT: = UART                                                                  AUXIN:  = Null Device                                                           AUXOUT: = Null Device                                                           LST:    = Null Device                                                                                                                                                                                                                           C>

In addition, I have verified that my CP/M 2, CP/M 3 and UZI280(and Hector Peraza's RSX280) operating systems all work under thenew Z280RC emulator by Michal Tomek.

The emulator (which runs under Linux/macOS and Windows MinGW)is available from

https://github.com/mtdev79/z280emu

Note that the UZI280 operating system still needs to be loadedfrom CP/M and not yet from the ZZmon monitor -

C>bootuzi                                                                       C:BOOTUZI  COM                                                                                                                                                  UZI280 is (c) Copyright (1990-96) by Stefan Nitschke and Doug Braun                                                                                             boot: 0                                                                         UZI280 version 1.12                                                             login: root                                                                     [root]/usr/root#

I'm working on adding support for the QuadSer module and direct boot capabilityfrom ZZmon to UZI280 and a CP/M RESET utility (to restart back to ZZmon).

They'll be added here soon.

Change the CP/M 2 cold-boot default drive to B: (since this is wherethe CP/M 2.2 system files are loaded). Updated only the "BIG" versionof theCPM22BIG.MACmonolithic source file - and there's a new IntelHEX loader file forCPM22BIG.HEXin the system/cpm22 subdirectory. No more "REQUIRES CP/M 3" messageswhen you type a "PIP" command! (and a warm-boot returns to the currentselected default drive).

Please note: The CP/M 3 system images I've made available are linkedwith Simeon Cran's ZPM3 replacement BDOS routines.

ZPM3 is a Z80 coded CP/M 3 compatible BDOS replacement which includes

• Bug fixes (the "Random Read Bug" and System Control Block sanity checks),

• Enhancements to the BDOS Parse (Function 152) to accept drive/userarea filespecs (like C1:FILE.DAT),

• New functions for file time-stamps manipulation - Get Stamp (Function 54),Use Stamp (Function 55) can retrieve and change a file's time-stamp, and

• Command-line history and WordStar(C)-style editing for Read ConsoleBuffer (Function 10).

You'll find more detailshereand I've added the ZPM3 distribution archive (includes sourcecode) in thesystem/zpm3/ZPM3S.ARCfile.

If you wish to revert to the Digital Research CP/M 3 BDOS, you'll need toselect it with the DRI-CPM3.SUB file and rebuild a new CPM3.SYS file (e.g.using the BIGBIOS.SUB build procedure from the BIOS source area).

I updated the CP/M 3 disk image to include the CP/M 2.2 BIOS sources(on drive B: user area 1), and included Infocom games and terminalset-up program (on drive D: in user area 0). Also, updated the IDEHD.MACCompactFlash driver module to match the latest version.

Get it fromz280rc-bigcpm-swab.img.gz

There's now an updated CP/M 3 banked memory system supporting 2048directory entries on the A: to D: drives (and if you require additionaldrives using the PARTN8 configuration option).

To be able to load CPM3.SYS from the revised drive layout, you'll needto install the new "BIG" CP/M 3 Loader fromCPMLBIG.HEXonto the Z280RC's CP/M 3 boot area using ZZmon V2.3 by uploading thisCPMLBIG.HEX Intel HEX file, and then write it to the boot track on theCompactFlash disk using the C3 command.

Next, you'll need to copy theCPM3BIG.SYSto the A: drive as CPM3.SYS, and install the CP/M 3 distribution files (becareful not to overwrite the new CPM3.SYS when you do this).

You can use cpmtools 'cpmcp' on a image file that's been transferred toa Windows, Linux or macOS system - using updated diskdefs fromhere, or by using the CP/M 2.2 system and XMODEM as detailed below

TinyZZ Monitor for Z280RC v2.3 18-Sep-2021>Boot1 - User Apps2 - CP/M 2.23 - CP/M 34 - RSX2805 - UZI280Select: 2 Press Return to confirm:Copyright 1979 (c) by Digital ResearchCP/M 2.2 for Z280RC20210918 w/2048 CF A:-D:a>b:b>pip xm.hex=con:[hz]

Send the Intel HEX load file for XMODEM from theXM27Z280.HEXfile in ASCII mode to PIP. After a while, the b> prompt will appear, thenload the HEX file to make XM.COM then download the XMODEM default configuartionfile using xmodem protocol (send it using your comms program) fromXMZ280RC.CFG -

b>load xmFIRST ADDRESS 0100LAST  ADDRESS 10FFBYTES READ    1000RECORDS WRITTEN 20b>xm xmz280rc.cfg /r/c/x3/z9/q

Now you have a working XMODEM (XM) command, use it to transfer files to theCP/M drive. You'll only need to use the /r (receive) or /s (send) optionsand maybe the /c (crc/checksum mode) from now on, if you have theXMZ280RC.CFG file on the current drive.

To save you some time, I have prepared an image of my CompactFlashCP/M drive partitions (A: thru D:) which is populated with a large rangeof software (compilers like Hi-Tech C, FORTRAN-80, BASIC-80, COBOL-80,RML ALGOL, TurboPascal plus the Z3PLUS Z-System and various editors andassemblers. The CP/M 3 BIOS source files are on drive C in user area 1.

Download the gzip'ed image fromz280rc-bigcpm-swab.img.gzuncompress it with gunzip then write it to your blank 128Mb or 256MbCompactFlash card using dd with the byte-swap option.

For example (when /dev/sdX is the CompactFlashdevice name under Linux)

gunzip z280rc-bigcpm-swab.img.gzsudo dd if=z280rc-bigcpm-swab.img of=/dev/sdX bs=512 count=65536 conv=swab

(substitute for /dev/sdX as appropriate on your system).

The changes I made to CP/M 2.2 to support 2048 directory entries (insteadof the original 512 directory entries) seem to be working.

I've updated the system/cpm22/CPM22ALL.MAC file to include a symboldefinition to enable this. Just change the symbol DE2048 to -1 andrebuild a new Intel HEX loader file (as I outlined below).

For your convenience, I've includedCPM22BIG.HEXthat you can load into ZZmon V2.3 (see below), then write thisto aNEW orSPARE CompactFlash card.

WARNING: THIS CHANGES THE CP/M DISK DIRECTORY AND FILE ALLOCATIONON EACH OF THE CP/M PARTITIONS - so don't do this to your previousworking CompactFlash card.

In addition to supporting a larger number of files, I've altered the diskallocation to use the previously unused track 63 on each of the A:, B:,C: and D: partitions. The latter three are now 8192 Kilobytes, whilethe A: drive has 1 reserved track for the system boot loaders (it is 8064 Kb).

Once you have uploaded CPM22BIG.HEX and issued the C2 command to writethe new CP/M 2.2 image to the boot track, format each of the drives onyourNEW CompactFlash drive using the XA, XB, XC, XD (and XE to clearthe RAMdisk). Now you can proceed to load the CP/M 2.2 programs onto theRAMdisk (drive E:) from theCPM22DRI.HEXfile.

TinyZZ Monitor for Z280RC v2.3 18-Sep-2021                                                                                                                                                                                                      >Boot                                                                           1 - User Apps                                                                   2 - CP/M 2.2                                                                    3 - CP/M 3                                                                      4 - RSX280                                                                      5 - UZI280                                                                      Select: 2 Press Return to confirm:                                              Copyright 1979 (c) by Digital Research                                          CP/M 2.2 for Z280RC                                                             20210918 w/2048 CF A:-D:                                                                                a>b:                                                                            b>dir                                                                           No file                                                                         b>e:                                                                            e>dir                                                                           E: ASM      COM : BIOS     ASM : CBIOS    ASM : DDT      COM                    E: DEBLOCK  ASM : DISKDEF  LIB : DUMP     COM : DUMP     ASM                    E: ED       COM : LOAD     COM : MOVCPM   COM : PIP      COM                    E: STAT     COM : SUBMIT   COM : SYSGEN   COM : XSUB     COM                    e>pip b:=e:*.*[v]                                                                                                                                               COPYING -                                                                       ASM.COM                                                                         BIOS.ASM                                                                        CBIOS.ASM                                                                       DDT.COM                                                                         DEBLOCK.ASM                                                                     DISKDEF.LIB                                                                     DUMP.COM                                                                        DUMP.ASMED.COM                                                                          LOAD.COM                                                                        MOVCPM.COM                                                                      PIP.COM                                                                         STAT.COM                                                                        SUBMIT.COM                                                                      SYSGEN.COM                                                                      XSUB.COM                                                                                                                                                        e>b:                                                                            b>stat b:                                                                                                                                                       Bytes Remaining On B: 8004k                                                                                                                                     b>stat b:dsk:                                                                                                                                                       B: Drive Characteristics                                                    65536: 128 Byte Record Capacity                                                  8192: Kilobyte Drive  Capacity                                                  2048: 32  Byte Directory Entries                                                   0: Checked  Directory Entries                                                 256: Records/ Extent   32: Records/ Block                                                            1024: Sectors/ Track                                                              64: Reserved Tracks                                                                                                                                          b>

Next up, I'll do the CP/M 3 system updates... stay tuned!

In preparation for increasing the number of directory entries on the CP/MCompactFlash drives A: to D:, I have uploaded my modifiedsource-code for CP/M 2.2 that can be built using Hector Peraza's ZSM4Macro Assembler. This also contains a (minor) fix to the RAMdisk sizeto match the Z280RC's memory (Bill Shen's original source was for the TinyZ280which supported larger SIMM72 DRAM modules, whereas the Z280RC has 2Mb ofstatic RAM).

To assist with the generation of a CPM22ALL.HEX in IntelHEX loader format, I've added a RELHEX utility that converts theassembler's .REL output file into .HEX to the utilities subdirectory. You'llfind the source for RELHEX12.MAChere,and a compiled CP/M binary)here.

To prepare CPM22ALL.HEX from the source inCPM22ALL.MACuse commands like -

ZSM4 =CPM22ALLRELHEX12 CPM22ALL

To install this, you may wish to grab and install thelatest ZZmon2 monitor V2.3 from Hector Peraza's GitHub repositoryathttps://github.com/hperaza/ZZmon2, clearmemory using the Z command, then uploadCPM22ALL.HEXto the running monitor. Finally, copy it to the CP/M 2 boot sectors usingthe C2 comand. For example -

TinyZZ Monitor for Z280RC v2.2 17-Sep-2021>Zero memory Press Return to confirm:>

Now send the Intel HEX file in ASCII mode. You should see a few rows of dotslike

>...........................................................................................................................................................................................................................................................................................................................................................................................................................................0X>Copy to CF0 - Boot & ZZmon1 - User Apps2 - CP/M 2.23 - CP/M 3Select: 2 Press Return to confirm:>Boot1 - User Apps2 - CP/M 2.23 - CP/M 34 - RSX2805 - UZI280Select: 2 Press Return to confirm:Copyright 1979 (c) by Digital ResearchCP/M 2.2 for Z280RC20180727 1.5 meg RAMdiska>

I'll post the new 2048 directory entry modifications in the next few days (afterI test them out).

I've included my cpmtools diskdef file entries in the "utilities"subdirectory. This allows you to perform file copies and manipulationsto an image file of the Z280RC's CompactFlash CP/M file partitions usingthe cpmtools utilities on Windows, macOS and Linux.

Please note that you need to create or write images that have thebytes swapped (the Z280RC interface has the bytes written in big-endianorder). The Linux 'dd' command has a 'conv=swab' option that does this.

The definition file can be downloaded fromhere.

After adding these entries to the system's diskdefs file you can manipulatedisk images by specifying the '-f z280rc-X' format (where X correspondsto the CP/M drive letter in lower case).

For example, from macOS or Linux -

# Copy CP/M partition from CompactFlash mounted on the device /dev/sdasudo dd if=/dev/sda of=z280rc-cf.img bs=512 count=131072 conv=swab# list the CP/M directory of the B: drive partitioncpmls -f z280rc-b -l z280rc-cf.img[directory of B: partition omitted]# copy a file to the CP/M E: drive in user area 10cpmcp -f z280rc-e z280rc-cf.img filename.txt 10:FILE.TXT# To write it back to CompactFlash use -#sudo dd if=z280rc-cf.img of=/dev/sda bs=512 count=131072 conv=swab

This is just a note about the way I set-up CP/M 3 on my Z280RC.

You might have noticed that I set the default login disk as drive C:.This is mainly as a convenience - as this is my working directory. Youcan change this using the GENCPM program when you do a system generationby answering the question with your desired default (some people likeit to be A:) -

C>gencpmA:GENCPM   COM  (User 0)CP/M 3.0 System Generation Default entries are shown in (parens).Default base is Hex, precede entry with # for decimalUse GENCPM.DAT for defaults (Y) ?Create a new GENCPM.DAT file (N) ? yDisplay Load Map at Cold Boot (Y) ?Number of console columns (#80) ?Number of lines in console page (#24) ?Backspace echoes erased character (N) ?Rubout echoes erased character (N) ?Initial default drive (C:) ? a:...(answer all remaining prompts with Return key)

Also, since this is the default drive upon booting, you'll need toplace a copy of SUBMIT.COM on this drive so you can use a PROFILE.SUBfile to tweak the system search path and device settings after boot-up.

If you have the CP/M 3 system files on drive A: then make theseaccessible from all user area and drives by ensuring they have theSYS attribute (and read-only if you're extra cautious). Do this using -

C>a:set a:*.com [sys ro]C>a:set a:help.hlp [sys ro]

(also you may wish to include various libraries and programming headerfiles) and then

C>a:pip c:=a:submit.com[r

Finally create a PROFILE.SUB like the following (create this with an editorif you prefer). As you see, I set my search path to use the currentdrive, the RAMdisk, drive C: and finally drive A:. I also copy theXMODEM configuration file to each disk in user 0 so I don't have tospecify the parameters to force it to use the console UART.

C>a:pip c:profile.sub=con:; C:PROFILE.SUB;; XMODEM default configuration to M:a:pip m:=a:xmz280rc.cfg[wrg0]a:set m:xmz280rc.cfg [sys ro]; Search path is current drive, RAMdisk, drive C and drive Aa:setdef * m: c: a: [order=(com,sub) display page uk temporary=m]; Use QuadSer port TTY3 at 115200 bps for Kermit (using the AUX: device)a:device aux:=tty3[115200]a:date^ZC>

(That last line is a Ctrl-Z to end the file).

With the system set-up like this, I no longer need to specifythe disk drive to run a program. Also, configure programs likeTurboPascal and WordStar with their SETUP programs to load theiroverlays etc from drive A: too.

Included a copy of CP/M KERMIT V4.11 (configured for CP/M-Plus) soyou can test the QuadSer ports.KERMIT.COMis available in the utilities subdirectory (or click the link).

Just set the AUX: port assignment and baud rate prior to running KERMITusing the DEVICE command (see below). When you use KERMIT'sconnectcommand, what you type will be sent out the QuadSer port, and anyreceived characters will be displayed on the console. If you connectthe port to another computer capable of running its version ofkermit inserver mode, you will be able to transfer files usingKERMIT'sget andsend commands.

Further details (and sourcecode) for KERMIT can be downloaded fromhttp://www.kermitproject.org/archive.html#cpm80

Built a modified version of the CP/M-Plus DEVICE utility to supportsubstituted baudrates. The new version will accept 28800, 38400,57600 and 115200 as speed values. The modified PL/M-80 sourcecode,DEVICE.COMas well as updated CP/M PlusHELP.HLP(and source in HELP.DAT) are in the utilities subdirectory.

Just copy DEVICE.COM and HELP.HLP to your system drive and set themwith the SYS attribute to make them available.

A>device tty3[115200A:DEVICE   COMPhysical Devices:I=Input,O=Output,S=Serial,X=Xon-XoffUART   NONE  IOS    TTY0   19200 IOS    TTY1   19200 IOSTTY2   19200 IOS    TTY3   115K2 IOSCurrent Assignments:CONIN:  = UARTCONOUT: = UARTAUXIN:  = TTY3AUXOUT: = TTY3LST:    = Null DeviceA>

Also, I added some notes regarding a hardware modification to the QuadSer4-port module that prevents spurious interrupts from floating inputson the serial Rx pins of each port. You'll find it in the QuadSer-notesfolder with aREADMEand photo (courtesy of Hector Peraza) of the mods.

And finally, I included anapplication notePDF retrieved from the Oxford Semiconductor pages on the Wayback machine.These were useful to me when I was writing the drivers for the OX16C9544-port UART chip.

Added CP/M Plus support for Bill Shen's QuadSer Rev1 4-port UART modulein RC2014 form-factor.

This is a UART module using the Oxford Semiconductor Ltd.OX16C954 rev B chip with 128-byte FIFOs for each receiver andtransmitter. It has 4 independent UART ports with program selectable baudrates between 50 and 115200 bps in a variety of framing formats. Higherspeeds are also possible - but not implemented for CP/M-Plus.

For hardware details see Bill Shen's pages at

https://www.retrobrewcomputers.org/doku.php?id=builderpages:plasmo:quadser:ec4z280rc

The configuration files now contain a "quadser" equate that you setto "true", along with a "use$device$io" equate to enable this support.

The current implementation uses polled I/O (and I intend to add supportusing interrupts soon).

With "quadser" enabled, four additional serial devices named TTY0,TTY1, TTY2 and TTY3 will be enabled. You can assign one or more ofthese to the console (CON:), auxiliary (AUX:) or printer device (LST:)using the DEVICE command. Speed settings can also be adjusted (see below).

For example, to specify TTY3 as the AUX device at 9600 bps use

A>device aux:=tty3[9600]

or to have the console input and output simultaneously on two devices(e.g. the Z280's UART and TTY0 at 19200 bps with XON/XOFF flow control) use

A>device con:=uart,tty0[19200,xon]

Since CP/M Plus was released, it is now common to use higher speeds thanthe 19200 bps maximum that the DEVICE command and internal CP/M datastructures allow. Therefore I have substituted four of the lesscommon data rates as follows -

    CP/M Old    Now        75      28800       134      38400       150      57600      1800     115200

Until I produce a modified CP/M Plus DEVICE program, you can specifyhigher speeds by using the corresponding old value on a DEVICE command.

For example, to use TTY3 at 115200 bps use -

A>device tty3[1800]A:DEVICE   COMPhysical Devices:I=Input,O=Output,S=Serial,X=Xon-XoffUART   NONE  IOS    TTY0   19200 IOS    TTY1   19200 IOSTTY2   19200 IOS    TTY3   1800  IOSCurrent Assignments:CONIN:  = UARTCONOUT: = UARTAUXIN:  = TTY3AUXOUT: = TTY3LST:    = Null DeviceA>

Pre-built versions of the various banked configurations can be foundin the system/bios280 subdirectory.

You can also download all the CP/M Plus BIOS files in the followingZIP file -

https://github.com/agn453/Z280RC/blob/master/system/bios280/bios280.zip

Fixed some erratic date/time setting under CP/M-Plus.

I've tweaked the DS1302 time-keeping chip routines in the BIOS CLOCKmodule (and the TIME.COM utility) to adjust the read/write timingto use a more accurate 1 microsecond serial timing for the 3-wireinterface.

I found the original DU-V88.LBR of Ward Christensen's Disk Utility(better late than never) and added it to the "utilities" subdirectory

Some more tinkering with I/O page selection, interrupt routine and wordaddress alignment. Also I found the missing .tar file with HiTech Cheader files and the UZI280 system libraries. I've put this UZISYTAR.LBRin system/uzi280-usrtar with the other .LBR files that can be extractedand written to the UZI partition using the XFRSYTAR.SUB submit file.When you boot UZI280 you'll need to extract this tar file below the rootdirectory using

/bin/shcd //bin/tar xvf /Tapes/uzi112s.tar

The HiTech C compiler now works.

/bin/shcd /usr/rootcat >hello.c <<EOF#include <stdio.h>main(){  printf("Hello world from UZI280 on the Z280RC!\n");}EOFcc hello.c./hello

I also added some utilities to the MKBOOT.SUB and COPYALL.SUB submit filesin the system/uzi280-xutils directory. This allows an UZI system partitionfor system recovery to be created (on either /dev/wd1 or /dev/wd2). Whenyou run (say) MKBOOT.SUB you'll need to specify a parameter to select thepartition. Use "2" for /dev/wd1 or "3" for /dev/wd2. After running thisyou can BOOTUZI and answer the boot: prompt with 2 or 3 (instead of 0) tostart the corresponding partition, Login as root and do a file system checkon the other (non-mounted) partitions - e.g.fsck /dev/wd0 to check theprimary UZI partition. You can also create mount-points and mount the otherfile systems for backup purposes -

/bin/shmkdir /disk0mount /dev/wd0 /disk0cd /disk0; tar cvf /Tapes/backup-wd0.tar .umount /dev/wd0

I've implemented support for the DS1302 timekeeper chip in UZI280to set the time-of-day and fixed an issue with I/O page selection affectingmaskable interrupts in my CompactFlash device support routine (IDECF.AS).You can fetch MACHDEP.C MACHASM.C and IDECF.AS from system/uzi280-kernel/and re-compile the kernel using MAKE - or download the UZIKERNL.LBR fileagain to get the complete kit of kernel build files. Fixing the aforementionedissues has introduced another problem with the UZI280 "ps" command which waspreviously working but now gives a "Can't read /dev/kmem: Error 0" which Iam investigating.

Also, a couple more UZI280 binary tar files for the HiTech C compiler (usesCPM emulation) and "User Binaries" have been added to system/uzi280-usrtaras well as in the CP/M library files UZICTAR.LBR and UZIUSTAR.LBR. UnderCP/M use NULU to extract the two .tar files and execute the XFRCTAR.SUBand XFRUSTAR.SUB to transfer them to the /Tapes directory on the UZIfile system partition. Extract these files under UZI280 using a commandlike the following -

/bin/shcd //bin/tar xvf /Tapes/uzi112c.tar/bin/tar xvf /Tapes/uzi112u.tar

Added UZI280 binaries to system/uzi280-bintar/UZIBNTAR.LBR. Use theXFRBNTAR.SUB submit file to transfer these to the /Tapes directory onthe UZI filesystem partition, then boot up UZI280, login as root (nopassword) and extract the tar files using something like the following

/bin/shcd /bin; for f in /Tapes/bin_0*.tar; do /bin/tar -xvf $f; done

CP/M utilities for manipulating library archives (.LBR files) and DiskUtility V8.8 (suitable for accessing the CP/M-Plus disk drivepartitions and sector view/editing) have also been added to the utilitiesfolder as NULU.COM and DU.COM

I've managed to modify the UZI280 operating system to boot up onthe Z280RC. There's been a few hiccups along the way (mainly dealingwith a mixture of word-count and byte-count DMA transfers) and the requirementfor using a modified version of the HiTech C V3.09 compiler and Z280library routines to build the system. I based my modifications on theUZI280 source code V1.12 for the Tillman Reh CPU280 system fromhttp://oldcomputers-ddns.org/public/pub/rechner/zilog/z280/uzi280/index.html

My modified sources are in the system/uzi280-kernel and system/uzi280-xutilsfolders. There are two CP/M library files UZIKERNL.LBR and UZIXUTIL.LBRthat can be transferred and extracted (using NULU.COM under CP/M-Plus) todifferent drives/user areas (I use E0: for the kernel files, F0: for theCP/M Utilities). A MAKEFILE in each can be used to build the librariesand UZI system image using the MAKE command. XUTILS.SUB will build twoCP/M utilities MKFS and UCP for creating a UZI partition and copying filesfrom CP/M. The log-file system/kernel/UZIBUILD.LOG is a transcript of thebuild process and start-up.

Still to-do is to copy the utilities and CP/M emulator onto the UZIpartition.

Squeeze a few more bytes from common memory. Add a CLOCK$50HZ settingto select between the 50Hz interrupt heart-beat clock using C/T 0 & C/T 1cascaded (see below) and a 128Hz clock using only Counter/Timer 0.

Implement and test Z280 on-chip device interrupts with a 20ms heart-beatcounter (a single word counter at BIOS+063h) using cascaded Counter/Timer0 and 1. These operate in timer mode and an interrupt is generated at50Hz. Enable this by setting both INT$ENABLED and USE$TIMER$INTERRUPTin the configuration file (CONFINT8.LIB has this enabled). Also removedthe dual banked testing version (CPM3BNK1.SYS) - but you may stillgenerate it if required using the BNK1BIOS.SUB submit command file.

Updated the DS1302 timekeeper chip TIME program (in the utilities directory)to support a Banked system (this makes adjusting the time-of-day easierthan using the CP/M-Plus DATE command).

Interrupt and Trap handling using Interrupt Mode 3 has been tested forSystem Calls and error traps (divison by zero, divide quotient exceptions,and memory access violations). Device interrupts are not yet implemented.Set the INT$ENABLED equate to TRUE to enable this in the configurationfile (CONFINT8.LIB is supplied with DEBUG still enabled). CPM3INT8.SYS isa bootable system image with this feature active.

Squeeze as much as possible out of the Banked system common memoryto maximise the size of the CP/M transient program area - resulting in61KB free for user programs. There's a new configuration setting toremove the Character I/O device support in BIOSKRNL and CHARIO modules.I've defaulted USE$DEVICE$IO to FALSE to only use the Z280 UART console(and free up common memory).

Also clean-up the conditional code to build a CPMLDR3.HEX loader. Now thesettings in the CONFLDR.LIB configuration correctly build the aforementionedloader that you can write to the CompactFlash boot tracks using the inbuiltZZMON monitor. Just upload the Intel Hex format file directly (e.g. usingthe File menu Send file... option of Tera Term VT) and do a "C3" commandto write it to the CP/M-Plus boot loader (sectors 1..15 of track 0).

Revised the banked memory layout to make the TPA and common memorycontiguous. The DMAXFR routine now works properly (so you may chooseto set USE$DMA$TO$COPY to TRUE to perform memory-to-memory transfersusing the Z280's on-chip DMA controller instead of the Memory ManagementUnit). Coming up next... Interrupts and System/User mode operation.

I examined the DMAXFR code with a view to fixing the defect regardingtransfers crossing the common memory address boundary. The modificationsincrease the size of the MOVE routine considerably (if I stick to thecurrent physical-logical memory addressing configuration). I've thereforedecided to not release updated DMA routines and instead will keep thememory management work-around in place for now. I may revise the memoryallocation in future though (and make the transient program area andcommon memory contiguous). Do not set the USE$DMA$TO$COPY configurationitem to TRUE in any of the configuration CONF*.LIB files for now.

USE$BIG$DRM now causes the extra drives E: thru H: to have 2048 directoryentries (the maximum for the 4096 byte block size). Updated IDEHD.MAC andthe CPM3*.SYS files. Also added a check for the maximum number of directoryentries for a given block size in the CPM3M80.LIB macro library (a versionof the Digital Research supplied CPM3.LIB that works with Microsoft's M80and Hector Peraza's ZSM4).

Also added an initialisation routine to the RAMDISK module to prompt forand format drive M: if it doesn't have a valid CP/M directory label.

I was running out of space/directory entries so I built a version ofBanked CP/M-Plus with eight 8MB CompactFlash drives. See the CONFBNK8.LIB,BANKED8.DAT, CPM3BNK8.SYS and BNK8BIOS.SUB files in the system/bios280directory.

Depending on the actual size of CompactFlash you have, play it safeand use at least a 128MB one if you use this (64MB is not the same as 64MiB).

Drives E: thru H: are configured with 1024 directory entries each. Anew configuration option USE$BIG$DRM enables 1024 directory entries(512 is the default for all other drives).

Hector Peraza's latest beta 11 of ZSM4 - a Z80/Z180/Z280 Macro-Assembleravailable athttps://www.retrobrewcomputers.org/forum/index.php?t=msg&th=93&goto=3700&#msg_3700found a typo in IDEHD which I fixed. Also went through and commented/removed superfluous lines from the BIOS sources. No object code changes -just cosmetic!

Added a modified version of Martin Eberhard's XMODEM 2.7 (for file transfervia the console serial port). This now includes routines to drive thebuilt-in Z280 UART directly. To select the internal routines use the /X3switch on the XMODEM command line (or make it the default by having theXMZ280RC.CFG in the default directory). You'll find these files in theutilities folder or you can download a ZIP containing them directly fromhttps://github.com/agn453/Z280RC/blob/master/utilities/xm27z280.zip

DMAXFR is not copying memory to memory when the source or destinationphysical address crosses one of the logical address bank boundaries.This is what has been causing interbank moves and disk I/O to failwhen more than two banks have been configured. (Bank 0 and Bank 1 workbecause there is no difference between physical and logical addressesup to the common boundary in Bank 1 - i.e. 01DFFFF). The CP/M 3 PIPprogram was using memory across this boundary - hence why a copy withverify was failing for large files.

Anyhow, I've modified the MOVE and Disk I/O routines to use the MMUto shuffle data between Banks (using just logical addresses) and everythingnow works. The Banked configuration (CONFBANK.LIB and BANKED.DAT) nowhas Debugging disabled and is using Banks 1..3 with a 60KB TPA (CPM3BANK.SYS).I've left the Bank0/1 version with the debugger enabled (CONFBNK1.LIBand BANKED1.DAT resulting in CPM3BNK1.SYS) and the non-banked (CONFNBNK.LIBand NONBANK.DAT in CPM3NBNK.SYS).

I'll update the DMAXFR routine soon to remedy the problem (described above)shortly. In the meantime enjoy a Banked version of CP/M-Plus on the Z280RC!

PS; I've included a ZIP file containing all of the system/bios280 files ashttps://github.com/agn453/Z280RC/blob/master/system/bios280/bios280.zipto assist those not wanting to download the whole GitHub repository.

Added USE$DMA$TO$COPY configuration equate. If set to FALSE then extendedmemory moves using the BIOS MOVE routine will use the memory management unitto copy data from one bank to another. Using this setting I confirmedthat the DMA transfers using the Z280's on-chip controllers were dodgy!I changed the DMAXFR routine in the BIOSKRNL module to in-line programthe DMA channel without looping.

The Banked memory version using just bank 0 and 1 (CPM3BNK1.SYS) now seemsto be working.

Added DEBUG capability to enter the debugger upon CTRL-P being typedat the console. Also made a special banked configuration that supportsonly two banks (bank 0 and 1) with directory hashing disabled and onlya single directory and data buffer for each drive in bank 0. Theresulting CPM3BNK1.SYS appears to be working (and I'm now convincedthere's a problem with CP/M 3 PIP corrupting buffers).

Also added CPM3ADD2.MAC which (when assembled and linked) will showinformation about the running system's BIOS, SCB and disk drive data(DPH and DPB).

Updated disk modules to use hard-coded disk parameter headers and diskparameter blocks with internal disk allocation vectors (rather thanletting GENCPM set these up). This is selectable via a USE$DISK$MACROSconditional equate in the CONF*.LIB files. Unfortunately, this had noeffect on the PIP file copying verification error under the bankedsystem. Non-banked and Loader configurations work fine!

My own version of a CP/M Plus BIOS for the Z280RC are in the "system/bios280"subdirectory.

There are submit files that build Non-banked (working), Banked (still hasproblems - see below*) and Loader .COM files (not yet integrated into theboot loader track on the CompactFlash drive).

The Y2K patched versions of the system page relocatable BDOS modules forCP/M 3 and the ZCPM3 system page relocatable compatible BDOS modules canbe selected using DRI-CPM3.SUB or USE-ZPM3.SUB prior to building everythingwith BUILDALL.SUB.

You'll need Hector Peraza's ZSM4 Z80/Z180/Z280 Macro-Assembler V4.0 beta 9or later as well as CP/M-Plus supplied LINK and GENCPM utilities too.

ZSM4 is available from the RetroBrew Computers Forum athttps://www.retrobrewcomputers.org/forum/index.php?t=msg&th=93&goto=3700&#msg_3700

The BUILDALL.SUB build procedure produces a CPM3NBNK.SYS and CPM3BANK.SYSsystem image that can be copied to the boot drive user area 0 as TEST.SYSand loaded via a special version of the CP/M Loader - TEST.COM

• Known problem with Banked version. I've left my debugging enabled, sothere is superfluous output for BIOS kernel routines, and a simple debuggeris invoked prior to starting CP/M's console command processor. This allowsmemory and register examination as well as memory management manipulation.The system seems to start fine, and you can navigate different drives andrun programs. If I try to use PIP to copy large files from one of theCompactFlash drives (A: thru D:) to the RAM disk (drive M:) I getverification errors and from then on there appears to be a memory corruption.

I suspect some issue with allocation of buffers (which I'll continue to lookat) - however, if you see an obvious error, please raise it as a GitHubissue.

Only an updated Non-Banked CBIOS3 and a CP/M utility to support the on-boardclock calendar timekeeping chip (TIME.MAC) have been added.The new CBIOS3 adds support for the DS1302 timekeeper to Non-BankedCP/M-Plus as well as character I/O changes for DEVICE support and a fixto the RAM disk size (Z280RC only has 2Mb memory)

I've also uploaded a zip file containing updated versions of CP/M-Plusbinaries that have been patched for Y2K and other updates.

I am working on a CP/M-Plus Banked Memory BIOS for the Z280RC and thiswill be added soon.