CPM Disk Tool
- 6 mins read
CPM Disk Tool
I’m currently working on implementing a CP/M for my small Z80 CPU. As a reminder, this involves a single Z80 CPU connected to a Raspberry Pi, with the latter emulating RAM, ROM, and IO devices.
I spent this weekend diving into the workings of CP/M disks. While there is a Unix tool available to create CP/M disk images , I’ve decided to create my own version using Python.
The project contains a class to manage the directory entries CPMDirectoryEntry, and another CPMDisk to deal with disk operations. The program also uses a disk definition file in order to generate different disk formats inspired by the Unix tool.
Finally, there is a tool disktool.py to manipulate the disk images.
Disktool
Example
python ./disktool.py -t 8Mb -f -d ./src/main -i ./img/disk_8.img -v
Sample output:
Disk: ./img/disk_a.img
Tracks: 77
Sectors per track: 26
Sector size: 128
Block size: 1024
Total blocks: 250 - (256000 bytes)
Reserved blocks: 6
Directory blocks: 2
Total usable blocks: 249 - (254976 bytes)
First usable block: 2 - (2, 12)
Sectors per block: 8
Directory start: 6656 - 00001a00
Data area start: 2048 - 00000800
Directory blocks: 2
Directory size: 2048
Directory max entries: 64
Size: 256256 bytes
Creating disk image ./img/disk_a.img of type 256k
Adding files from directories: ['./src/main']
** Adding file: ASM.COM
** Adding file: basic.com
** Adding file: CRC.COM
** Adding file: DDT.COM
** Adding file: DUMP.COM
** Adding file: ED.COM
** Adding file: LOAD.COM
** Adding file: MBASIC.COM
** Adding file: PIP.COM
** Adding file: STAT.COM
** Adding file: SUBMIT.COM
** Adding file: SURVEY.COM
** Adding file: SYSGEN.COM
** Adding file: XSUB.COM
** Adding file: ZDE.COM
Directory Listing:
--------------------------------------------------------------------------------------------------------------
Entry Usr Ext Filename Type Rec Blocks Size
--------------------------------------------------------------------------------------------------------------
0 0 0 ASM COM 40 - 02 03 04 05 06 07 08 09 00 00 00 00 00 00 00 00 - 8.00 Kb
1 0 0 BASIC COM 80 - 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 - 16.00 Kb
2 0 1 BASIC COM 61 - 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 00 00 00 - 13.00 Kb
3 0 0 CRC COM 29 - 27 28 29 2a 2b 2c 00 00 00 00 00 00 00 00 00 00 - 6.00 Kb
4 0 0 DDT COM 26 - 2d 2e 2f 30 31 00 00 00 00 00 00 00 00 00 00 00 - 5.00 Kb
5 0 0 DUMP COM 04 - 32 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 1.00 Kb
6 0 0 ED COM 34 - 33 34 35 36 37 38 39 00 00 00 00 00 00 00 00 00 - 7.00 Kb
7 0 0 LOAD COM 0e - 3a 3b 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 2.00 Kb
8 0 0 MBASIC COM 80 - 3c 3d 3e 3f 40 41 42 43 44 45 46 47 48 49 4a 4b - 16.00 Kb
9 0 1 MBASIC COM 3e - 4c 4d 4e 4f 50 51 52 53 00 00 00 00 00 00 00 00 - 8.00 Kb
10 0 0 PIP COM 3a - 54 55 56 57 58 59 5a 5b 00 00 00 00 00 00 00 00 - 8.00 Kb
11 0 0 STAT COM 29 - 5c 5d 5e 5f 60 61 00 00 00 00 00 00 00 00 00 00 - 6.00 Kb
12 0 0 SUBMIT COM 0a - 62 63 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 2.00 Kb
13 0 0 SURVEY COM 0d - 64 65 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 2.00 Kb
14 0 0 SYSGEN COM 0c - 66 67 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 2.00 Kb
15 0 0 XSUB COM 06 - 68 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 1.00 Kb
16 0 0 ZDE COM 80 - 69 6a 6b 6c 6d 6e 6f 70 71 72 73 74 75 76 77 78 - 16.00 Kb
17 0 1 ZDE COM 04 - 79 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 - 1.00 Kb
--------------------------------------------------------------------------------------------------------------
Total entries: 64 - Used entries: 18
Usage
Usage: disktool.py [-h] -t TYPE [-d DIR [DIR ...]] [-a ADD [ADD ...]]
[-e EXTRACT [EXTRACT ...]] [-f] [-s] [-db DUMP] -i IMG
[-v]
Options:
-h, --help Show this help message and exit
-t TYPE, --type TYPE Type of disk to create (required)
-d DIR [DIR ...], --dir DIR [DIR ...]
Directory with files to add
-a ADD [ADD ...], --add ADD [ADD ...]
Add files to disk
-e EXTRACT [EXTRACT ...], --extract EXTRACT [EXTRACT ...]
Extract files from disk
-f, --format Format disk
-s, --show Show directory
-db DUMP, --dump DUMP
Dump a block (hex)
-i IMG, --img IMG Image file. With -f image will be created (required)
-v, --verbose Verbose output
Description:
This program allows you to create, modify, and inspect disk images.
Examples:
Create a new disk image:
disktool.py -t 256k -i new_disk.img -f
Add files to an existing disk image:
disktool.py -t 256k -i existing_disk.img -a file1.txt file2.txt
Extract files from a disk image:
disktool.py -t 256k -i disk.img -e file1.txt file2.txt
Show the directory contents of a disk image:
disktool.py -t 256k -i disk.img -s
Dump a specific block from the disk image in hexadecimal:
disktool.py -t 256k -i disk.img -db 0
Note: The --type and --img options are required for all operations.
Disk definitions are stored in the diskdef file, it is similar but not the same as the Unix tool.
Example for a 256k disk image: 77 tracks, 26 sectors per track, 128 bytes per sector, 1024 bytes per block, 242 directory sectors, 64 directory entries, 2 reserved tracks.
def 256k
tracks 77
sectors 26
bytes_sector 128
blocksize 1024
bsh 3
blm 7
dsm 242
drm 64
off 2
end
Create disk image with content files included in ./scr/main as ./img/disk_a.img
python ./disktool.py -t 256k -f -d ./src/main -i ./img/disk_a.img -v
Add files to disk image
python ./disktool.py -t 256k -i ./img/disk_a.img -a ./src/main/file1.txt ./src/main/file2.txt -v
Also you might use the classes in your own code, for example:
import cpm_disk
disk = CPMDisk("TDISK02.DSK",
77, # 75 tracks
26, # 26 sectors per track
128, # 128 bytes per sector
1024, # 1024 bytes per block (1 block = 8 sectors)
3, # bsh - block shift
7, # blm - block mask
242, # dsm - max data blocks
64, # drm - max directory entries
2) # off - reserved tracks
initialize_disk()
Or a custom tool as dir.py
from argparse import ArgumentParser
from cpm_disk_def import CPMDiskDefinition
if __name__ == "__main__":
parser = ArgumentParser()
parser.add_argument("-i", "--img", help="Image file to create", required=True)
parser.add_argument("-t", "--type", help="Type of disk to create", required=True)
parser.add_argument("-v", "--verbose", help="Verbose output",
action="store_true")
args = parser.parse_args()
diskdef = CPMDiskDefinition()
diskdef.print_defs()
disk = diskdef.get_disk(args.type, args.img)
disk.disk_info()
disk.read_directory()
disk.list_directory()
if args.verbose:
disk.disk_map_visual()
disk.disk_map_free()
disk.dump_block(0)