CP/M-80

CP/M 8080 hardware emulator on Stellarpad, ESP8266 and ESP32, using r65emu.

• Digital Research manual for CP/M 2.2
• useful info here
• cpmtools for linux
• software: z80.eu, cpmarchives, cpm.z80.de

Creating disks

Install cpmtools:

$ sudo apt install cpmtools

Create a disk image:

$ mkfs.cpm foo

Copy files into it:

$ cpmcp foo bar baz 0:

Put it into disks/:

$ mv foo disks

Edit disks/drivemap.txt to assign the new disk to a drive.

Use of SD card storage is recommended where possible.

CP/M in ROM

A previous system was a "CP/M in ROM".

This consisted of two files (see the directory system):

• CBIOS.ASM the "skeletal CBIOS" from Appendix B of the CP/M 2.2 manual
• CPM22.ASM CP/M 2.2 itself, from here

Each of these was assembled to its corresponding .bin file by asm8080 and from there to .h by makerom:

$ asm8080 CPM22.ASM
$ makerom -bp CPM22.h cpm22 > cpm22.h

The ROMs were loaded at addresses 0xe400 (cpm22) and 0xfa00 (cbios), leaving 57kB free.

Booting CP/M from disk

The next system loads CP/M from disk, as nature intended. The boot disk cpma.cpm comes from the excellent emu8080.

A modified 8080 port-mapping supports the BIOS found on this disk (see io.cpp). The file system/bios8080.asm (from z80pack) is compatible with this port-mapping scheme --- it's a near ancestor of the BIOS in emu8080.

The system tracks for this are broken out into system/system.bin. This can be used to create bootable disk-images as follows:

$ mkfs.cpm -b system.bin foo.cpm

z80pack

A later implementation used a bootable system image produced by putsys from z80pack in conjunction with mkfs.cpm from cpmtools.

This BIOS has support for hard-disk images (4MB).