Appendix B: PC Serial Ports
Serial Ports Under Windows 3.1
Unlike the DOS-only world of yesterday, today’s multitasking environments like
Windows permit the microprocessor to communicate with up to four active
serial port devices at the same time (COM1 through COM4). For example,
under Windows, if you are using a serial mouse (on COM1 ) within a terminal
emulator program which operates a data modem (on COM2), while using a fax
board (on COM3) to transmit or receive a fax "in the background," you are
using three serial port devices simultaneously. You might even wish to make a
phone call using PassageWay Solution (on COM4) at the same time, bringing
the total up to four simultaneously active serial port devices.
The fact that Windows permits this kind of powerful multitasking does not
guarantee that the underlying PC hardware can support this level of operation,
at least without some customizing at the hardware level. Since some PCs can
support it by default (for example, those which support IRQ sharing), Windows
doesn’t prohibit you from configuring your system and attempting tasks like the
one in the previous paragraph. Unfortunately, most PCs cannot support this
operation by default and the most likely result of attempting the above
scenario is "hanging" the PC due to an IRQ conflict. On such systems, using
COM1 along with COM2 is generally fine (recall that these devices have
unique IRQs by default), but the addition of COM3 or COM4 causes the
system to fail.
Fortunately, Windows 3.1 permits complete customization of all parameters
involving serial ports through the Control Panel, including configuring
nonstandard I/O port addresses and IRQs (that is, values different from those
in the table – these parameters can be viewed and/or modified by selecting
the desired port in the Control Panel’s "Ports" applet, selecting the "Settings..."
button, then selecting the "Advanced..." button). This flexibility offers the
opportunity of salvation for owners of PCs which do not support IRQ sharing
who require the use of three or more COM ports simultaneously.
B-6
Summary of Contents for Partner 18
Page 1: ......
Page 21: ...xvi ...
Page 28: ...Installing and Setting Up PassageWay Solution Figure 2 1 PassageWay Solution Components 2 3 ...
Page 65: ...Installing and Setting Up PassageWay Solution 2 40 ...
Page 93: ...Using AT TBuzz 3 28 ...
Page 96: ...Using AT TCall Figure 4 1 Untitled AT TCall Window 4 3 ...
Page 97: ...Using AT TCall Figure 4 2 Components of an AT TCall Window 4 4 ...
Page 100: ...Using AT TCall Figure 4 4 Desktop with 10 20 Quick Dials and Card Hidden 4 7 ...
Page 101: ...Using AT TCall Figure 4 5 Desktop with 25 50 Quick Dials and Card Displayed 4 8 ...
Page 102: ...Using AT TCall Figure 4 6 Desktop with 25 50 Quick Dials and Card Hidden 4 9 ...
Page 144: ...Using AT TCall Figure 4 26 Printed Cards With and Without the Notes 4 51 ...
Page 177: ...Using AT TCall 4 84 ...
Page 181: ...Using AT TSet Figure 5 2 Components of the AT TSet Window 5 4 ...
Page 247: ...Using Log Viewer 6 20 ...
Page 250: ...Using AT TConnect Figure 7 1 AT TConnect Window 7 3 ...
Page 252: ...Using AT TConnect Figure 7 2 Events Log Dialog Box 2 When finished select the OK button 7 5 ...
Page 265: ...Using AT TConnect 7 18 ...
Page 287: ...Troubleshooting 9 18 ...
Page 289: ...Appendix A Menu Trees Figure A 1 AT TBuzz Menu Tree A 2 ...
Page 290: ...Appendix A Menu Trees Figure A 2 AT TCall Menu Tree A 3 ...
Page 291: ...Appendix A Menu Trees Figure A 3 AT TSet Menu Tree A 4 ...
Page 292: ...Appendix A Menu Trees Figure A 4 Log Viewer Menu Tree A 5 ...
Page 293: ...Appendix A Menu Trees Figure A 5 AT TConnect Menu Tree A 6 ...
Page 305: ...Appendix B PC Serial Ports B 12 ...
Page 311: ...Glossary GL 4 ...
Page 318: ...560 201 103 AT T 1993 AT T ...