1. usbserial.zip Driver
2. DOSBOX.TXT File Contents

DOSBOX.TXT Driver File Contents (usbserial.zip)

SohoBasic USB Serial Converter DOS Box Support

Version 2.0

This version of the serial converter drivers provides support for programs 
running in a DOS session under Windows 95 or Windows 98. DOS box support 
is enabled from within the Device Manager. Right-click the 'My Computer' 
icon on the desktop and select 'Properties'. Click on the Device Manager 
tab.

From within the Device Manager, click the '+' sign beside the 'Ports' 
section. This will expand that section to show all of the communication 
ports on your machine. Select the 'USB Serial Port' and click 
'Properties'. Click on the 'DOS Box' tab. Click on 'Enable DOS Box 16550 
emulation' to select DOS support.

After selecting the DOS Box emulation, you will have to choose the COM 
port that DOS uses to communicate with the serial converter. This can be 
the same COM port that the converter is already using. Select the COM port 
name from the drop-down list.

DOS programs communicate with serial ports using an interrupt (IRQ) and an 
I/O address. There are a limited number of IRQs available for use - the 
typical machine only has 14. Most of these are already used by other 
systems inside your computer. For instance, your hard drive system and 
your mouse will usually each use an interrupt.

The following table shows the standard IRQ and I/O assignments for COM1 - 
COM4. These values should work with most DOS programs.

  Port    IRQ     I/O	
  --------------------
  1       4       03F8
  2       3       02F8
  3       4       03E8
  4       3       02E8

COM1 and COM3 share IRQ4. This means that COM1 and COM3 cannot be used 
simultaneously, since a program cannot tell which port is actually 
receiving data. Since COM2 and COM4 also share an interrupt they have the 
same restriction. Unless DOS box support is enabled, the serial converter 
does not normally use an interrupt, so this does not affect it.

However, if DOS support is turned on, a USB DOS Serial Port Emulator will 
be installed. This emulator uses both an IRQ and an I/O address and is 
affected by the normal COM port restrictions.

To avoid having a conflict, it is possible to assign a COM port a 
different interrupt or I/O address. In order to do this you should select 
the COMX option. The DOS box emulator will choose an IRQ and I/O address 
that do not conflict with your other hardware. You can view the settings 
it chose from the 'DOS Box' tab in the properties page.

If you wish to modify these settings, select the 'USB DOS Serial Port 
Emulator' device and click 'Properties'. Go to the 'Resources' tab and 
uncheck the 'Use automatic settings' checkbox. Then select either the 
'Input/Output Range' or the 'Interrupt Request' and click 'Change Setting' 
to enter your own value. However, since you are overriding the automatic 
selection your choice may conflict with other hardware installed in your 
computer.

If you select the COMX option you will need to configure your DOS program 
to use non-standard IRQ and I/O addresses. Check the manual or 
instructions that came with your program for information on setting these 
parameters. Since many programs cannot access non-standard COM ports, try 
to use COM1 - COM4 if possible.

On some computers, after you have enabled DOS box support, Windows will 
detect an IRQ conflict between the built-in COM ports and the USB Serial 
Port. In this case it may reassign the resources that the built-in COM 
port is using. It will also occasionally renumber the built-in COM port so 
that it is past COM4. Either of these actions may cause your existing 
programs to stop working with the built-in COM port. In this case try 
resetting the original COM port and using a different COM port name for 
the serial converter DOS box emulation.

To reset the original COM port temporarily disable DOS box support by 
unchecking the 'Enable DOS Box 16550 emulation' checkbox. Then select the 
built-in COM port and click 'Remove'. After restarting your computer 
Windows should redetect the original COM port and assign it the correct 
name and resources.

Due to the limited number of interrupts, it may not be possible to find a 
free IRQ in your computer. In this case DOS box emulation may not work 
without a conflict.