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Configuration Files


Configuration files are used to keep all the parameters of an assembly of VMB devices in one central place. If possible, all devices that connect to the motherboard should read one and the same configuration file when starting. As a further convenience, the motherboard can be configured - using this same configuration file - to start all the devices that belong to the assembly, binging up (and later down) a consistent set of devices.


In a configuration file, a parameter specification is given by a line that starts with the parameter name followed by one or more spaces (or tabs) and the value of the parameter. Parameter names are not case sensitive. Values are either numeric values, given either as decimal or hexadecimal numbers (e.g. 0xFF), or strings. String values extend from the first non blank character to the last non blank character of the line. Sometimes it is necessary to enclose string parameters in double quotes (for instance if it starts with a space).

As a rule, all paramters that can go in a configuration file can also be used on the command line using the parameter name as "long" options (prefixed with a minusminus) and vice versa. Most "long" options, especially those that are used often, are also available as short, single letter options (prefixed with a single minus). Short options are for use on the command line only, they dont work in configuration files. As an example, you can get a list of all parameters of a VMB device by starting it with the "-?" option (short) or the "--help" option (long). As with any option, you could use the long otion "help" also in a configuration file - but obviously, in this case the option is intended for interactive use.

Using the Windows version, you can also select "Configuration" from the "Help" menu to get a Text windows displaying all parameters and their current settings.

Starting a Device

When a device is started, it does a quick check of its command line to find out if contains a configuration file either in the form "-c filename" or "--config filename". If either one is present, there is no further search for any other configuration file and the command line is used as described below. If the command line does not specify a configuration file, the current working directory is searched for a file named "default.vmb". If such a file exists, it is read. So you can keep all the files belonging to an assembly of devices in one directory and place the default configuration in this file. If there is no such file in the current working directory, the directory where the devices executable is located will be searched for a "default.vmb" file. If found, this file will be processed if not, no configuration file is processed.

After processing a possible "default.vmb" configuration file, the device will process the command line. This way, parameters specified on the command line take precedence over parameters specified in the default file. The parameters on the command line are processed form left to right,. Later parameters can overwrite settings by earlier parameters. This rule holds also for a configuration file specified on the comand line. Its content will overwrite paramters earlier on the command line (or in the file) and can be overwritten themselves by parameters later on the command line.

Typically, only the motherboard is started - either in Unix style from the command line or by a doubleclick. Under Windows, the installation program mentioned below will set a file association betwen ".vmb" files and the motherboard. So doubleclicking a configuration file will start the motherboard with this configuration file as command line parameter. All the rest of the devices that form the desired assembly are then started by the motherboard as specified in the configuration file (using the "exec" option).

Common Parameters

Most devices will need one of the following parameters:


User Interface



Executing Commands


Looking at the list of parameters and the intended use in a central configuration file, you might wonder how to specify the address of a device in a file that is shared by all the devices in an assembly. The answer is: by designating parts of the configuration file for specific devices using a conditional.

A conditional has the simple form:

#if devicename

When a device reads a configuration file and it encounters a conditional, it will check its device name against the devicename given in the conditional. If the names are equal it will continue to process the input. If the names are not equal it will simply skip over the input until it finds the #endif. By default, the name of a device it the name of the program. So a section like

#if ram
address 0x10000000
size      0x400000

will apply to the ram device, giving 4MB Ram at address 0x100000000. If you have two ram modules as part of your assembly, you can use --define highram or -D highram on the command line when starting the second ram device and the configuration file then contains this:

#if ram
address 0x10000000
size      0x400000

#if highram
address 0x80000000
size      0x400000


When configuration files get more and mor complex, it is a good idea to sprinkle in some comments. Do do so, just begin a line with a hashmark #, then the rest of the whole line will be ignored.


Currently, configuration files know only two variables: #FILE# and #PATH#. Any occurence on the sting #FILE# in a parameter value will be replaced by the full absolute filename of the configuration file itself; any occurrence of #PATH# will be replaced by the full absolute path (including the last "/" or "\" character) of the configuration file. A typical use of such a variable is

exec rom -c "#FILE#"

here the motherboard will start the rom device with the same configuration file by explicitely specifying it on the devices command line. Note the double qoutes. Especially under Windows, filenames often contain spaces. Without the double quotes, the -c option would only take the first part of the string #FILE'#, up to the first space as argument value. An other example is:

#if rom 
address 0x0 
file "#PATH#linux/vmlinux.img" 

Here the rom device gets the rom image vmlinux.img from the linux subdirectory of the directory that contains the configuration file.