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DiskImage-CPM22.md

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How to make CP/M DISK Image

Overview

This system emulates a CP/M disk on a microSD Card. Disk images are managed as files on the microSD Card, so if multiple image files are in it, they are considered independent disk drives.

The microSD Card must be formatted with FAT32.

Disk image file naming conventions

  • DISKnn.IMG (nn is 00-15, corresponding to drives A:-P:)

DISK00.IMG, which is drive A: must contain the CP/M system (CCP+BDOS). Due to memory limitations, the BIOS on this system only supports up to 5 drives. Therefore, the actual usable drives are up to 00-04.

The disk image must match the DPB supported by the BIOS. When generating a disk image with cpmtools, specify the following format defined in diskdefs.

diskdef sdcard
seclen 512
tracks 256
sectrk 64
blocksize 8192
maxdir 256
skew 0
boottrk 1
os 2.2
end

In this format, one track is reserved for boottrk, and the CP/M system (CCP+BDOS) is stored here on the system disk (IMAGE00.IMG).

The SD Card access library in ATmega128 firmware can only write to files that already exist. For this limitation, all data (approximately 8GB) of the disk image file must be generated in advance.

How to generate a disk image file

z80/cpm22/image/Makefile supports the following image generation.

CP/M2.2 system disk

Generate DISK00.IMG based on CP/M 2.2 BINARY.

make

When using z80/cpm22/sys/CPM.SYS

If you want to use CPM.SYS built based on the source code of CP/M 2.2 ASM SOURCE, change z80/cpm22/image/Makefile as follows.

CCPBDOS   = ../sys/CPM.SYS
#CCPBDOS  = $(CPM22_DIR)/CPM.SYS

Empty disk image

EMPTY.IMG will be generated, so copy it to DISKnn.IMG and use it, or create a new image based on this.

make empty

ZORK I/II/III

make zork

ZORK.IMG will be generated, so copy it to DISKnn.IMG and use it.

Any disk image

Using cpmcp

You can create any image by using cpmtools' `cpmcp' to transfer any file onto the disk image.

For example, there are many CP/M binary files at CP/M software Download site. You can also pick up the files and create a disk image that you want.

The following example transfers all files in ./tmp to an empty disk image and assigns it to the B: drive as DISK01.IMG.

cpmcp -f sdcard EMPTY.IMG ./tmp/*.* 0:
cp EMPTY.IMG DISK01.IMG

Using shell script mkimg.sh

By using ../z80/cpm22/image/mkimg.sh, you can directly generate an image without using EMPTY.IMG.

  • Usage: 
    Usage: mkimg.sh <fmt> <img> [files ...]
      <fmt>: format defined in /etc/cpmtools/diskdefs
      <img>: image file name
      [files ...]: CP/M files (optional)
  • Example: 
    $ ./mkimg.sh sdcard test.img tmp/zork/*.*
1021+0 records in
1021+0 records out
8364032 bytes (8.4 MB, 8.0 MiB) copied, 0.149639 s, 55.9 MB/s
0:
file_id.diz
zork1.com
zork1.dat
zork2.com
zork2.dat
zork3.com
zork3.dat

CP/M software Download site