Appendix B: PC Serial Ports
associated with them (recall that most PCs require the IRQs used by each
active device to be unique to avoid conflicts). To understand why, it's useful
to recall what the PC world was like before the widespread availability of
products like Windows. When the architecture of the current generation of
PCs was first being designed (for the IBM PC/AT), the concept of multitasking
was not nearly as important in the PC marketplace as it is today.
Consequently, since DOS (before Windows) did not permit multiple
applications to run simultaneously (with the notable exception of certain
specialized programs such as mouse drivers), there was little need to provide
a mechanism by which several serial ports could be operated simultaneously.
Consequently, the strategy used was to conserve IRQs by assigning the same
IRQ to more than one COM port (that is, the COM1 and COM3 ports were
both assigned to IRQ4, and the COM2 and COM4 ports were both assigned to
IRQ3). Then, under the assumption that at most two serial ports would be
active simultaneously (for example, COM1 and COM2, which have unique
IRQs), conflicts would not occur.
B-5
Содержание Partner 18
Страница 1: ......
Страница 15: ...Contents C Appendix C Running AT TBuzz in Export via Paste Link DDE Mode C 1 Glossary GL 1 Index Index i x ...
Страница 21: ...xvi ...
Страница 28: ...Installing and Setting Up PassageWay Solution Figure 2 1 PassageWay Solution Components 2 3 ...
Страница 65: ...Installing and Setting Up PassageWay Solution 2 40 ...
Страница 93: ...Using AT TBuzz 3 28 ...
Страница 96: ...Using AT TCall Figure 4 1 Untitled AT TCall Window 4 3 ...
Страница 97: ...Using AT TCall Figure 4 2 Components of an AT TCall Window 4 4 ...
Страница 100: ...Using AT TCall Figure 4 4 Desktop with 10 20 Quick Dials and Card Hidden 4 7 ...
Страница 101: ...Using AT TCall Figure 4 5 Desktop with 25 50 Quick Dials and Card Displayed 4 8 ...
Страница 102: ...Using AT TCall Figure 4 6 Desktop with 25 50 Quick Dials and Card Hidden 4 9 ...
Страница 144: ...Using AT TCall Figure 4 26 Printed Cards With and Without the Notes 4 51 ...
Страница 177: ...Using AT TCall 4 84 ...
Страница 181: ...Using AT TSet Figure 5 2 Components of the AT TSet Window 5 4 ...
Страница 247: ...Using Log Viewer 6 20 ...
Страница 250: ...Using AT TConnect Figure 7 1 AT TConnect Window 7 3 ...
Страница 252: ...Using AT TConnect Figure 7 2 Events Log Dialog Box 2 When finished select the OK button 7 5 ...
Страница 265: ...Using AT TConnect 7 18 ...
Страница 287: ...Troubleshooting 9 18 ...
Страница 288: ...Appendix A Menu Trees This appendix contains the menu trees for the PassageWay applications A 1 ...
Страница 289: ...Appendix A Menu Trees Figure A 1 AT TBuzz Menu Tree A 2 ...
Страница 290: ...Appendix A Menu Trees Figure A 2 AT TCall Menu Tree A 3 ...
Страница 291: ...Appendix A Menu Trees Figure A 3 AT TSet Menu Tree A 4 ...
Страница 292: ...Appendix A Menu Trees Figure A 4 Log Viewer Menu Tree A 5 ...
Страница 293: ...Appendix A Menu Trees Figure A 5 AT TConnect Menu Tree A 6 ...
Страница 305: ...Appendix B PC Serial Ports B 12 ...
Страница 311: ...Glossary GL 4 ...
Страница 318: ...560 201 103 AT T 1993 AT T ...