2400/9600 BPS Faxmodem (250-3027) Ports Setting Faxback Doc. # 4871 Communications Port Selection: IMPORTANT: Your fax/modem has a set of jumpers that configure it for use on a particular COM port (1 through 4). The setting of the COM port jumpers on your fax/modem is extremely important. The fax/modem will operate properly in all respects ONLY if there are no COM port or interrupt conflicts. Read the following instructions carefully to decide how to configure the COM port jumpers on your fax/modem. Then, if necessary, change the jumpers so that your fax/modem will work. If you received software with your fax/modem, please check the directory where the program is installed to see if it contains a program called ZPORTS. If it does, run ZPORTS before installing your fax/modem. ZPORTS will suggest which COM port to use. If you do not have ZPORTS, or if your fax/modem does not work after installing it in the port suggested by ZPORTS, read the following information: On the great majority of IBM-compatible XT/AT computers, there are one or more external serial ports built-in to the motherboard. If there are two, they are almost always COM1 and COM2. You cannot use your internal fax/modem on a COM port of the same number that already exists internally or externally, even if the internal or external ports are not actually in use. The reason is that no two devices (a mouse, scanner, modem or even a non- used physical port) can share a COM address. In addition to this is the assignment of an interrupt, or IRQ. The standard IBM-compatible XT/AT design calls for COM1 and COM3 to share IRQ4, and COM2 and COM4 to share IRQ3. As with the COM address, no two devices may share an IRQ. The 250-3027 fax/modem has the ability to use non-standard IRQ's to help alleviate such conflicts. However, it is necessary for the telecommu- nications program you are using to recognize these non-standard setups. Note: If your software has a particular need to use COM1 or COM2 (dictated by a particular communications program and by some Windows configurations), most computers allow you (either via hardware settings or a setup program) to either disable external serial ports or to reconfigure COM2 to COM4, for example, which may allow you to use the fax/modem on COM2. If you configure your fax/modem for COM3 or COM4, be sure that the software you are using is able to address that port. Most popular communications programs should be able to address COM3 and COM4. There are a few other circumstances you may run into: If you have configured the fax/modem for COM4 and it does not work, even though you are not using COM2 or COM4 for anything else (either hardware or device drivers), you may have to disable COM2, either via hardware settings (jumpers on the computer's Main Board or an I/O card) or a setup program. The same applies to interference between COM3 and COM1. Finally, it is possible that your computer has another device (for example, a network card or game card) that is using the same address or the same interrupt as the fax/modem, even though that other device is not using a COM port. This situation, too, will cause the fax/modem not to work. In this case, you will have to use a different COM port, or reconfigure the other device so that it does not conflict with the fax/modem in terms of COM port, interrupt, or address. Summarizing: Your PC must not have two devices trying to use the same COM port or interrupt. If another device conflicts in any of these ways with your fax/modem, you must either (1) use the jumpers to select a new COM port, (2) disable a conflicting COM port, (3) remove or reconfigure the conflicting device, or (4) reconfigure the fax/modem to use non-standard IRQ's. Example: The majority of installations are straightforward: a serial mouse on COM1 with IRQ4, a fax/modem on COM2 with IRQ3. However, if there is another device already on IRQ3, whether or not it uses a COM port, either reconfigure that device to use a different IRQ (preferred) or reconfigure the fax/modem to use a different IRQ (if your software supports it). For reference, here is a list of the IBM-compatible IRQ assignments: IRQ # Standard Assignment 0 System clock 1 Keyboard 2 Normally open (AT machine use as cascade, can often still be used) 3 Normally open (unless COM2/4 present) 4 Normally open (unless COM1/3 present) 5 LPT2 6 Floppy drive 7 LPT1 Note: DOS does not use interrupts to print, therefore, IRQ 5 and 7 are usable as well. For an explanation of how to select the COM and IRQ assignments for these options, refer to Faxback Doc. # 4874. (dtc-07/28/93)