This
is a special feature of the VScom driver. In older versions it was simply
called overspeed. This panel is prepared for other future extensions, whatever
they will be.
Overspeed opens the possibility to get other speeds than the application
requested for. The application requests a certain speed; this is multiplied
with the value defined in here. The result is set as the real speed.
Possible factors range from 0.125 (1 divided by 8) up to 32 in steps
of 0.125. Of course you can not get a speed which is higher than the maximum
speed of the port (921600).
The normal value is 1 of course, and it should be left there. This
is a dangerous feature. With a modem you very easy can get a speed the
modem can not handle.
- Wrong: Overspeed is set to 8. The modem has a maximum interface rate of 460800 Baud. When the application requests 115200, the result is 921600 Baud. The modem can not handle this.
- Wrong: Overspeed is set to 2. The application requests 38400, the result is 76800. Even when this is below the maximum speed of the modem, it does not recognize this speed in many cases. Operation is not possible.
- Wrong: Modem detection may fail, because of wrong settings.
- Correct: The application is limited to 19200. Overspeed my be 6 or 12 to get 115200 or even 230400 with a modern modem.
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This defines the emulation for the DOS-Box.
This special panel is reserved for future use. It is not functional with the actual driver!
It will be possible to define a virtual base address and a virtual IRQ for DOS programs. Also the port may get an entry in the BIOS address table in the DOS-box.
The DOS-program will act as if there is a real UART with these properties, but all handling is done by the driver. This avoids the risc of conflicts with Interrupt sharing etc.
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