CHAPTER 7: Troubleshooting
When using Windows 3.1, only two ports at any time are functional.
How to identify the problem: Verify that all ports have a separate interrupt, or if sharing interrupts, only one device is using the IRQ at a time.
Solution: Change the IRQs so that each port has its own unique interrupt (the preferred setting) or close each port before trying to open the next.
Reason: The Windows communication driver does not support simultaneous operation of shared interrupts.
In Windows 3.1, the mouse hangs or moves erratically.
How to identify the problem: Verify that the mouse is not sharing an interrupt with any other port or device.
Solution: Change the IRQ of your mouse port so that it does not share an interrupt. Most mice only operate on either COM1 or COM2 using IRQ 4 and 3 respectively. This is a limitation of the mouse driver.
Reason: A mouse is an interrupt “hog.” Any movement or
The application requires that the Modem Control signals be “on” or “active,” but they aren’t connected in my cable.
How to identify the problem: Check the pinout of your cable and the device you are connected to.
Solution: The unused modem control signals are biased ON on the board.
MSD (Microsoft® Diagnostics) doesn’t report the ports on the RS422/485 Serial Interface Plus.
How to identify the problem: Verify that the RS422/485 Serial Interface Plus addresses are correctly set.
Solution: Use the program SETCOM (found on your utility diskette) to install your additional ports.
Reason: MSD only reports the serial ports found by the BIOS. Older BIOS install only COM1 or COM2. Newer BIOSs will install up to four ports, but only if the traditional COM port addresses are used.
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