CP/M v2.23

Overview

CP/M Boot Process

Booting CP/M occurs in two phases:

1. Using the original AFI Floppy Disk control software, read in an inverted boot sector, check it contains at 0x0000 the control code 0x02 + “IPLPRO”, then pass control to the encapsulated boot loader
2. Load, starting at 0x9C00, the CCP, BDOS and CBIOS. The CBIOS now takes control and applies a different disk format and uses different FDC Controller logic (ie. re-inverts the data).

CBIOS

In order to create a CBIOS you have to provide the following API methods:

Thus in order to write the CBIOS, the following firmware sub-modules need to be coded:

All this functionality takes space and it has been apportioned as follows:

CPM Disk Drives

The ordering of the drives is shown in the following table:

Features

Besides the standard BIOS functionality, the following features have been added to the CBIOS.

• Real Time Clock with 50mS granularity
• Interrupt driven keyboard with buffer and auto repeat.
• Tri-mode key lock, Normal, Caps Lock, Shift Lock
• Ansi Terminal Functionality
• Re-targettable Floppy Disk drives of size 1.44M, 720K & 320K
• Re-targettable ROM drives of size 240K (changeable via config)
• Re-targettable SD Card 16Mb Hard disks.
• Exit to Monitor via SHIFT+GRAPH+BREAK.

Building CPM

To accomplish it you need several tools and at the moment it is quite a manual process.

Paths

For ease of reading, the following shortnames refer to the corresponding path in this chapter.

Tools

Z80 Glass Assembler - A Z80 Assembler for converting Assembly files into machine code.
samdisk - A multi-os command line based low level disk manipulation tool.
cpmtools - A multi-os command line CP/M disk manipulation tool.
CPMToolsGUI - A Windows based GUI CP/M disk manipulation tool.
z88dk - An excellent C development kit for the Z80 CPU.
sdcc - Another excellent Small Device C compiler, the Z80 being one of its targets. z88dk provides an enhanced (for the Z80) version of this tool within its package.

Software

Building the software images can be done by cloning the repository and running some of the shell scripts and binaries provided.

The CP/M system is built in 4 parts,

1. the cpm22.bin which contains the CCP, BDOS and a CBIOS stub.
2. the banked CBIOS which has its primary source in a 4K ROM and 4 banked 2K ROMS. These
   are generated for adding into the RFS Banked Monitor ROM and the Banked User ROM.
3. upto 2 (currently) Read Only CPM ROM Drive's which can be assigned to any CP/M drive
   letter.
4. conversion of the binaries generated in 1. and 3. into sectored MZF images suitable
   for adding directly into the Rom Filing System as just another program.

All of the above are encoded into the assemble_cpm.sh bash script which can be executed as follows:

cd <software>
tools/assemble_cpm.sh

The script is currently set to generate 1 Read Only CPM ROM Drive. To add a second CPM ROM Drive, follows these instructions:

1. Edit the <tools>/make_cpmdisks.sh script and change the
   variable:
   from BUILDCPMLIST="cpm22 CPM_RFS_1"
   to   BUILDCPMLIST="cpm22 CPM_RFS_1 CPM_RFS_2"

   change the variable:
   from SOURCEDIRS="CPM_RFS_[1] CPM[0-9][0-9]_* CPM_MC_5 CPM_MC_C? CPM_MC_D? CPM_MC_E? CPM_MC_F? CPM[0-9][0-9]_MZ800*" to
   to   SOURCEDIRS="CPM_RFS_[1-2] CPM[0-9][0-9]_* CPM_MC_5 CPM_MC_C? CPM_MC_D? CPM_MC_E? CPM_MC_F? CPM[0-9][0-9]_MZ800*"
   
2. Create a directory (if it doesnt exist): 
   <CPM>/CPM_RFS_2

3. Fill the directory with required CPM files to be placed in the ROM.

4. Build the image by running the make_cpmdisks.sh script or as part of the sequence of commands listed below.

In order to use CPM, it is necessary to create the MonitorROM and USERROM images which can be programmed into the 2x512KByte Flash RAMS. Issue the following commands to build CPM along with all the RFS, ROMS and Applications in ROM:

cd <software>
tools/assemble_cpm.sh
tools/assemble_rfs.sh
tools/assemble_roms.sh
tools/make_cpmdisks.sh
tools/make_roms.sh
tools/make_sdcard.sh

The output of the above commands are ROM images <roms>/MROM_256.bin and <roms>/USER_ROM.256.bin which must be flashed into 512Kbyte Flash RAMS and inserted into the sockets on the RFS adapter.

The CPM disk images can be found in <CPM>/1M44/RAW for the raw images or <CPM>/1M44/DSK for the CPC Extended format disk images. These images are built from the directories in <CPM>, each directory starting with CPM* is packaged into one 1.44MB drive image. NB. In addition, the directories are also packaged into all the other supported disks as images in a corresponding directory, ie <CPM>/SDC16M for the 16MB SD Card drive image.

The SD Card image can be found in <roms>/SHARP_MZ80A_RFS_CPM_IMAGE_1.img which contains the RFS Disk image <roms>/SHARP_MZ80A_RFS_IMAGE_1.img at the start followed by seven CPM format drive images which, as per above, are stored in <CPM>/SDC16M/RAW. These images are built from the directories in <CPM> but are manually added in to the final images by hardcoding in the script make_cpmdisks.sh.

The applications which are stored in the ROM drives are located in the <MZF> directory. Copy any applications you want into this directory then issue the following command to process them into sector rounded images stored in the <MZB> directory.

cd <software>
tools/processMSFfiles.sh

The actual applications which are built into the ROM are selected in the <tools>/make_roms.sh script. This script lists all the applications required and it will pack as many as space permits into the ROM. To ensure your application appears in ROM, add it to the top of the list (just the filename not the .MZF extension), ie:

Edit the file <tools>/make_roms.sh
Locate the line: ROM_INCLUDE=
Below this line, add your application in the format: ROM_INCLUDE+="${MZBPATH}/<YOUR APPLICATION>.${SECTORSIZE}.bin"
ie. ROM_INCLUDE+="${MZB_PATH}/A-BASIC_SA-5510.${SECTORSIZE}.bin:"
Save the file and run the commands above to build the MonitorROM and USERROM's.

Disk Formats

As I found out, there are 100’s of CP/M disk formats and the Sharp series alone implements 2-3 per machine. In deciding on what format to use for this implementation of CP/M I looked at the existing formats. Not having access to original Sharp MZ80A disks and with them being in inverted non-standard format anyway, the MZ80B being similar to the MZ80A but slightly higher capacity, the MZ800 being a hybrid and the MZ80K being low capacity, I opted to use standard formats for 1.44MB, 720K 3.5” Floppies, the same physical format as the Sharp MZ80A disks and the ROM based 240K Rom Drive.

The formats I am using can be manipulated by cpmtools using the following diskdefs definitions, place the above into the diskdefs file located with the cpmtools or CPMToolsGUI to use:

   # 320K Disk for the MZ80A - Same format as the MZ800
   # but implements a cylinder in uniform manner (ie. 1 cyl
   # = 1 track x 2(heads) where as the MZ800 implements as 
   # 160 tracks, 80 x Head 1 0->79 then 80 x Head 2 80->159.
   diskdef MZ80A-A
     seclen 256
     tracks 40
     sectrk 32
     blocksize 2048
     maxdir 64
     skew 0
     boottrk 1
     os 2.2
   end
   
   # A standard format 1.44Mb Floppy format for the MZ80A
   diskdef MZ80A-1440
     seclen 512
     tracks 80
     sectrk 36
     blocksize 2048
     maxdir 128
     skew 0
     boottrk 0
     os 2.2
   end
   
   # A standard format 720K Floppy format for the MZ80A.
   diskdef MZ80A-720
     seclen 256
     tracks 80
     sectrk 36
     blocksize 2048
     maxdir 128
     skew 0
     boottrk 0
     os 2.2
   end
   
   # A 240K Rom Filing System ROM Drive image.
   diskdef mz80a-rfs
     seclen 128
     tracks 15
     sectrk 128
     blocksize 1024
     maxdir 32
     skew 0
     boottrk 0
     os 2.2
   end

   # A 16Mb fixed disk SD Card Image.
   diskdef MZ80A-SDC16M
     seclen 512
     tracks 1024
     sectrk 32
     blocksize 8192
     maxdir 512
     skew 0
     boottrk 0
     os 2.2
   end   

Creating a CPM Disk

To convert the image, use one of the following:

For 1.44MB Drives use:
./samdisk copy <RAW IMAGE FILE, ie. CPM00_SYSTEM.RAW> <DSK IMAGE FILE, ie.CPM00_SYSTEM.DSK> --cyls=80 --head=2 --gap3=78 --sectors=36 --interleave=4
Samdisk will automatically recognise the format from the size of the file, ie. 1474560 bytes

For 720K Drives use:
./samdisk copy <RAW IMAGE FILE, ie. CPM00_SYSTEM.RAW> <DSK IMAGE FILE, ie.CPM00_SYSTEM.DSK> --cyls=80 --head=2 --gap3=78 --sectors=36 --size=2 --interleave=4
Samdisk will automatically recognise the format from the size of the file, ie. 737280 bytes

For the MZ80A 320K Drives use:
./samdisk copy CPM00_320K_SYSTEM.RAW CPM00_320K_SYSTEM.DSK --cyls=40 --gap3=78 --head=2 --sectors=16
Samdisk will automatically recognise the format from the size of the file, ie. 327680 bytes

The RFS ROM Drive does not need conversion, the RFS functionality assumes a raw image.

NB. Dont use Samdisk v4, it has a bug where it will place a random sector at the start of the disk. Many hours debugging were lost due to this bug. Best to use
samdisk v3.8.8

The above samdisk commands create an Amstrad CPC Extended DSK format image which can be read and processed by Lotharek HxCFloppyEmulator or tools used to write physical floppy disks.

Extract MZ80A CP/M Disks

Under construction.

Extract MZ80K CP/M Disks

Under construction.

Extract MZ80B CP/M Disks

Under construction.

Extract MZ800 CP/M Disks

Use samdisk to convert the EDSK (Extended DSK format created for the Amstrad CPC Machine, most MZ800 disks appear to be in this format) into a RAW image.

  samdisk copy <MZ800 DISK NAME>.DSK <MZ800 DISK NAME>.RAW --cyls=40 --head=2 --sectors=8 --size=256

Run the following bash commands to convert the RAW format disk obtained above into something which can be read by CPMTools.

   mv <MZ800 DISK NAME>.RAW workingfile.raw
   > total
   dd if=workingfile.raw of=total count=8192 bs=1
   for i in $(seq 8192 8192 327680); do 
     dd if=workingfile.raw of=blob skip=$i bs=1 count=4096
     cat blob >> total
     echo $i
   done
   for i in $(seq 12288 8192 327680); do
     dd if=workingfile.raw of=blob skip=$i bs=1 count=4096
     cat blob >> total
     echo $i
   done
   mv total <MZ800 DISK NAME>.RAW

You will need the following diskdefs definition in order to read the data from the processed RAW image.

   # Definition for the MZ800 CP/M Boot Disk. The reserved
   # track is in inverted data format but this is skipped in
   # CPM Tools.
   diskdef mz800-BOOT
     seclen 256
     tracks 80
     sectrk 16
     blocksize 2048
     maxdir 64
     skew 0
     boottrk 1
     os 2.2
   end

   # Definition for the MZ800 CP/M Data disk. No reserved tracks.
   diskdef mz800-DATA
     seclen 256
     tracks 80
     sectrk 16
     blocksize 2048
     maxdir 64
     skew 0
     boottrk 0
     os 2.2
   end

CP/M Archives

I have removed the CP/M archives from github as it is not the place to store/archive files. Please download the zip file should you require them and unpack in your /software directory.

The files in the archive are selected programs and come from various CP/M archives and are assembled in directories with the naming convention CPM[0-9[0-9]_. Also included (and due credit and (C) for his work in assembling the archive) is from Grant Searle's MultiComp computer which is multiple computers in one (or multiple CPU types) and one of it's modes is to run CP/M. The archive of Grant's is excellent and an ideal base to use CP/M on the MZ80A.

To build the archives into a set of 1.4MB Floppy images suitable for use in a 3.5” Drive or Floppy Emulator, run the command:

cd <software>
tools/make_cpmdisks.sh

The disks will be created in the directory: <CPM>/1M44/DSK.

This script also builds the 16MB SD Card drive images using a combination of the archives. The combination is hardcoded inside the script.

CP/M Manuals

Credits

Where I have used or based any component on a 3rd parties design I have included the original authors copyright notice within the headers or given due credit. All 3rd party software, to my knowledge and research, is open source and freely useable, if there is found to be any component with licensing restrictions, it will be removed from this repository and a suitable link/config provided.

Licenses

This design, hardware and software, is licensed under the GNU Public Licence v3.

The Gnu Public License v3

The source and binary files in this project marked as GPL v3 are free software: you can redistribute it and-or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

The source files are distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.