This repository contains the original CP/M 3 BIOS source files, plus my modified files to support either the original Digital Research Inc. supplied CP/M 3 BDOS modules, or Simeon Cran's ZPM3(1) replacement BDOS modules for the Z80-MBC2 single board computer (see https://hackaday.io/project/159973-z80-mbc2-4ics-homemade-z80-computer for details)
The original BIOS modules (extracted from the Hackaday microSD SD-S220718-R280819-v1.zip file) have been translated from the original RMAC-style 8080 Assembly language format into Zilog Z80 mnemonics and can be assembled using the Microsoft M80 Macro Assembler or (my preferred) Hector Peraza's ZSM4 Macro Assembler(2).
Updated the Z80-MBC2 XMODEM.COM to the latest version of Martin Eberhard's XMODEM version 2.9. The new version is in the "bios" subdirectory as XMODEM.COM and the new configuration file XMODEM.CFG, with the Zilog Z80 assembler source-code in XM29MBC2.MAC. This version has a new /K option that controls the amount of file buffer space used for the file transfer. The XMODEM.CFG file supplied has as a default /K20 - which limits the buffer to 20KB (which is sufficient to allow for the slow file writes to the microSD file system and prevent timeouts).
The old version has been renamed to XMODEM27.COM (and XMODEM27.CFG) respectively.
Modify the XMODEM program to use half the available memory for buffering the file to send or receive. The relatively slow access time to read or write a file to the microSD card was causing a time-out and abort when sending or receiving large files while the file was being read/written.
Some minor updates to allow debugging the banked BIOS memory move module (XMOVE and MOVE). Two additional submit files are included to build banked system images (DRI3DBG.SYS and ZPM3DBG.SYS) that can trace the calls to the BIOS XMOVE and MOVE routines by outputting messages to the console. I used these to track down an issue with the Digital Research banked BIOS that may cause memory corruptions. The issue doesn't seem to occur if you use the ZPM3 banked BDOS replacement (from ZPM3.SYS).
Include latest Arduino sketches for the Z80-MBC2 board.
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Z80-MBC2-ATmega32A-PU is a copy of the unmodified release S220718-R240620_IOS using the ATmega32A-PU chip. This includes support for CollapseOS.
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Z80-MBC2-ATmega1284P-PU contains my modifications for the ATmega1284A-PU chip. This was forked from https://github.com/HomebrewMicros/Z80-MBC2-ATMEL1284 and also contains the CollapseOS updates too.
To build the sketches under the Arduino IDE with XMODEM extended buffering support, you must modify the MightyCore board definitions to include extra symbol definitions for SERIAL_RX_BUFFER_SIZE=256 and SERIAL_TX_BUFFER_SIZE=64. The file arduino-changes-MightyCore-2.0.5.readme has a context diff for the version I'm using.
Also, I've updated ZSM4.COM to the latest release.
Tidy up the build files. BUILDDRI.SUB now builds a DRI3.SYS file from the Digital Research supplied Resident BDOS modules, and BUILDZPR.SUB produces ZPM3.SYS from Simeon Cran's ZPM3 replacement BDOS modules.
Also included the source-code to the Z80-MBC2 version of XMODEM and AUTOEXEC.ASM (from the SD card src/CPM_3_Utils folder) and cleaned up stray NUL and CTRL-Z characters from the end of text files.
Firstly, I have attempted to re-construct the distributed CP/M 3 system image file (CPM3-128.SYS).
The build procedure submit file BUILD.SUB does a long-winded build of the original Intel 8080 sourcecode modules (.ASM files) and my translated sourcecode modules (.Z80 files). Both the original and translated build files produce byte-identical BIOS images. However, even using the original GENCPM.ORG configuration, I'm unable to get a byte-for-byte exact copy of the distributed banked system CPM3-128.SYS. Most likely this is due to differences in un-initialized data areas.
Secondly, I have modified the Z80 sourcecode modules to -
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Incorporate some byte-saving optimizations (replace absolute jumps with relative ones) in the BIOSKRNL module.
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Moved the sign-on message text into banked memory (it is only used on start-up) in the BOOT module.
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Fixed the ?TIME routine to transfer all 7 bytes of data from the IO processor (ATmega32A). Although there's no routine to return it, the temperature reading in degrees Celsius is now exposed via a global variable @TEMPC.
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Removed unused common stack space from the CHARIO module.
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Added XMOVE capability to the MOVE module. This allows programs like BOOTSYS to load a replacement system image into the correct memory banks for testing.
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Added a zero checksum vector size to invocations of the DPH macro since all drives are permanently mounted - in the VDISK module.
My modified Z80 sourcecode is in various .MAC modules and can be built into a system image by the BUILDZPR.SUB submit file (which selects the ZPM3 replacement BDOS routines).
The resulting system gives a 61KB TPA
Z80-MBC2 - A040618
IOS - I/O Subsystem - S220718-R280819
IOS: Found extended serial Rx buffer
IOS: Z80 clock set at 10MHz
IOS: Found RTC DS3231 Module (22/10/19 13:38:59)
IOS: RTC DS3231 temperature sensor: 25C
IOS: Found GPE Option
IOS: CP/M Autoexec is OFF
IOS: Current Disk Set 2 (CP/M 3.0)
IOS: Loading boot program (CPMLDR.COM)... Done
IOS: Z80 is running from now
Z80-MBC2 CPMLDR BIOS - S180918
CPMLDR3 - CP/M V3.0 Loader
Copyright (C) 1982, Digital Research
RESBIOS3 SPR FA00 0600
BNKBIOS3 SPR 5600 2A00
RESBDOS3 SPR F400 0600
BNKBDOS3 SPR 2800 2E00
61K TPA
Z80-MBC2 128KB (Banked) CP/M V3.0 with ZPM3
Z80-MBC2 BIOS Modules: S200918, S210918-R170319, S220918-R180319, S290918,
S170319
A>setdef * a: [order=(com,sub) display uk]
If you don't wish to rebuild everything from sourcecode, the file ZPM3.SYS can be copied to CPM3.SYS on the A: drive prior to rebooting with a RESET.
ZPM3 has a built-in command editor that uses WordStar compatible keystrokes. CTRL-X and CTRL-E advance and goback each command, and CTRL-Y is used to remove a command line. CTRL-S and CTRL-D are cursor left and right and CTRL-G is delete current character. Full documentation is on the Tesseract Volume 93.
If you wish to download all modules in a single convenient file then
fetch the
https://github.com/agn453/Z80-MBC2-master/blob/master/MBC2BIOS.LBR library
and extract the contents to an empty directory using the CP/M NULU.COM utility
with a command like nulu d:MBC2BIOS.LBR -e *.* from the CP/M prompt.
All the files (and assembly listings) are in the bios directory.
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(1) ZPM3 sourcecode can be obtained from the Tesseract RCPM+ archives in Volume 93 at http://www.classiccmp.org/cpmarchives/cpm/mirrors/www.triton.vg/TesseractRCPM+Catalog.html#vol93
(2) The source-code for ZSM4 Z80/Z180/Z280 Macro Assembler may be obtained from https://github.com/hperaza/ZSM4 and I have included a working CP/M binary for ZSM4 version 4.1 (ZSM4.COM) and the PDF documentation (ZSM4.PDF)