Instruction manual

The Drive Activity LED should light up for about a minute and a half while the format program fills

the CP/M disk with 0xE5. When the light goes off, the monitor prompt should re-appear. The disk is

now ready for the CP/M files to be placed on it.

Putting the CP/M System Files onto the disk

The CP/M file system set up in the CBIOS reserves the first 2 tracks of each disk for the system files.

This is important, because every time CP/M is started, whether from a cold boot or a warm restart, the

system is loaded from the disk into memory. You can see this code in the CBIOS listing, in the

WBOOT subroutine. Sector 1 of track 0 is reserved for boot code (not used in this system), and the rest

of the sectors in tracks 0 and 1 have a memory image of the operating system.

To set this up properly, we need to use the CBIOS routines for disk writing to put the system onto the

disk from memory. For this, I have written a putsys program. It is similar to the format program, in that

is uses the CBIOS disk write subroutines, but differs in that it copies data from memory, from address

0xE400 to the end of memory, and places it on the disk.

So first, we need to put CP/M into memory. Remember that the cpm22.sys file has the assembled code

for the CCP and BDOS, with a dummy BIOS jump table at the end. It is important that we load this file

into memory first, then load the z80_cbios.bin file on top of it, so that the true BIOS jump table will be

present in memory. We again use the monitor command bload to place these files into memory at the

proper places. The cpm22.sys file is placed at address 0xE400, and z80_cbios.bin at 0xFA00:

2 With some experimentation I have found that it is not absolutely necessary to format the disk before installing CP/M. If

you do not format the disk, when you list the CP/M disk directory, you may get a series of blank entries or jumbled

strings displayed. You can fix this by erasing the entire directory with an ERA *.* command.