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WINDOWS
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ALLOV10A
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ALLOPORT.TX_
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ALLOPORT.TX
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1994-05-18
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2KB
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50 lines
Standard PCs have only two IRQ lines for serial ports, therefore
COM3 must share COM1's IRQ line and COM4 must share COM2's
IRQ line. Unfortunately, two devices using the same IRQ
line can't be active at the same time. COM3 can't be used for
a printer or modem if a serial mouse is active on COM1, for
example. Likewise, COM4 can't be used if a serial mouse is
active on COM2. In other words, if you have four COM
ports and a mouse is attached to one of them, you do not
have three COM ports available for other devices, you only
have two. The COM port that shares the IRQ line being
used by the mouse is not usable.
The following table shows what ports are available for other
devices in a conventionally configured PC, XT, or AT when a
serial port mouse is present on a multiple-port system:
Serial port mouse on Ports available for other devices
_____________________ _________________________________
COM1 or COM3 (IRQ4) COM2 or COM4 (IRQ3)
COM2 or COM4 (IRQ3) COM1 or COM3 (IRQ4)
Windows system.ini file holds all settings for the environment
devices, including the communication drivers and serial ports parameters.
The table below shows the recommended general seetings for serial ports from
COM1 to COM4, as a starting reference, minimizing the chances of conflicts.
system.ini
[386Enh]
COM1Base=3f8h
COM2Base=2f8h
COM3Base=3e8h
COM4Base=2e8h
COM1Irq=4
COM2Irq=3
COM3Irq=4
COM4Irq=3
IMPORTANT:The IRQ's must be compatible with the Hardware setup (Refer to
the hardware installation manual). It means if you have a sound board or a
scanner installed, you have to check the actual IRQ's used and choose the
appropriated setup for the system.ini.
At this point it should be emphasized that YOU have to find your own optimal
setup because there are no software and hardware standards for
communication devices.