The debug kernel normally only accepts commands enetered at the debugging console. However, during system initialisation it will accept commands entered into a text file, which if used, must be called KDB.INI and reside in the root directory of the boot drive.
The KDB.INI file is read after the kernel has loaded and the kernel symbols are loaded and the system is running in protect mode.
Warning:
The content of the KDB.INI file is somewhat sensitive. If you make a syntax or format error then you may hang the system and have to re-boot from installation diskettes to recover.
On most systems the use of a KDB.INI file is not required to establish correct operation of the COM port and should be avioded.
Each command must be terminated with a <CR><LF> pair except the last in the file.
The KDB.INI is most easily created using:
COPY CON: KDB.INI
Enter the commands you require, using the <RETURN> key after each command except the last. For the final command, teminate it using the sequence: Ctrl-Z <RETURN>.
Note:
Use of an editor for creating KDB.INI may not be suitable if the <CR><LF> sequence cannot be suppressed from the last line.
The following example hows how to select COM3 at 1200 bps, with DTR held high and to prepare the debugger to intercept any ring 2 or 3 traps.
.b 1200t 3e8
O 3ec 1
vsf *
g
Notes:
Since the default arithmetic base for the debugger is hexadecimal a t suffix is required if the COM port speed is specified in decimal as in the example.
We have assumed a standard port address asignment for COM3, namely 3e8 for data register and 3ec for control register.
The VSF command causes the debugger to intercept all ring2 and ring3 traps and give control to the debug console.
The G command is required unless you want to enter the debugger as soon as the kernel has entered protect mode, loaded its symbol file and executed the KDB.INI file.