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Firstly the AMSDOS command |CPM loads the first sector of track 0 into the CPC464.
On a system disc this sector has been arranged to be a program which then loads the
rest of the system tracks into memory. Various checks are performed to determine that
the system tracks contain valid CP/M software and to calculate where in memory to
load them.
Part of CP/M is permanently in ROM inside the DDI-1 disc interface, the rest is
loaded into RAM. In the standard configuration 39.75k of RAM is left for transient
programs, with 2k of that used by the Console Command Processor which is loaded
from the system tracks whenever the Direct Console Mode is re-entered.
3.3 Configuration Sector.
During the loading process, when CP/M is first activated, various system parameters
are loaded from a special sector within the system tracks. These parameters include the
Sign-On (wake-up) message, special keyboard codes required etc. The SETUP utility
is provided to customise the configuration sector to your requirements.
3.4 Console control codes.
In the CP/M environment a variety of special key operations are used to control
program flow. These keystrokes replace the action of the [ESC]ape key used in
AMSTRAD BASIC, although some applications packages may re-instate the [ESC]
ape key with some of its former power.
[CTRL]S
halts the screen output from CP/M. Type any character to resume.
[CTRL]C
typed at the start of a line returns control to the Direct Console Mode.
Many utilities and applications programs will also recognise this as a
request to abandon the program.
[CTRL]P
hardcopy toggle. Turn on/off log of all screen output to printer.
[CTRL]Z
end of text.
3.5 Logging in a disc
Unless special action is taken by the CP/M program (as FILECOPY does for example)
then CP/M will not allow you to write to a disc unless it has been 'logged in'.
Furthermore the type of disc format (SYSTEM, DATA OR IBM) is only re-
determined when a disc is logged in. For drive A this takes place whenever CP/M
returns to the Direct Console Mode, or when [CTRL]C is typed at the A> or B>
prompt. For Drive B this takes place the first time that the disc in drive B is accessed
after drive A has been logged in.
Should you try writing to a disc that has not been logged in, the error message Bdos
Err on <DRIVE> : R/O will be displayed. Press any key to continue. If the
changed disc was also of a different format then A read or write error will occur. Type
C to continue.
AMSTRAD Disc Drive & Interface DDI-1 Manual Chapter 3.2