ATT Passageway For Partner Communications System User Guide

Appendix A: Menu Trees
Figure A-3. AT&TSet Menu Tree
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Appendix A: Menu Trees
Figure A-4. Log Viewer Menu Tree
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Appendix A: Menu Trees
Figure A-5. AT&TConnect Menu Tree
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Appendix B: PC Serial Ports
Overview
This appendix provides detailed information about PC serial ports, including
background information about what they are and how they work, how Microsoft
Windows 3.1 manages them, how to resolve problems using COM3 or COM4
under Windows, and how to choose serial port hardware that is well-suited to
PassageWay Solution. If you are familiar with serial port terminology (for
example, I/O port addresses, IRQs, etc.), you may wish to skip over the
background section. If...

Appendix B: PC Serial Ports
Background
Serial ports (also sometimes referred to as communications ports or COM
ports) are hardware interfaces which permit your PC’s microprocessor to
communicate with peripheral devices using a communications standard called
RS-232 (hence, serial ports are also sometimes referred to as RS-232 ports).
Many common computer accessories make use of serial ports, including serial
mice, modems, serial printers, and the PassageWay adapter.
Under DOS (and Windows, which works...

Appendix B: PC Serial Ports
represents a small region of the microprocessor’s input/output memory space
which is used to pass data back and forth to the serial port. This memory
region acts something like a mailbox: outgoing mail (data from the
microprocessor to be transmitted to the peripheral device) is placed in the
mailbox by the owner (the microprocessor) to be picked up by the mail carrier
(the serial port hardware) for subsequent delivery to the destination party (the
peripheral device). In turn,...

Appendix B: PC Serial Ports
denoted IRQ0, IRQ1, and so on, up through IRQ15), the microprocessor must
take the appropriate action for the device associated with that IRQ. If there is
a mix-up, or if more than one device attempts to use the same IRQ at the
same time, a conflict occurs, and the outcome is often unpredictable and
usually undesirable (for example, the computer may hang). Because IRQs
are a limited resource, some newer PCs support IRQ sharing, a hardware
mechanism which permits more than one...

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, its 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...

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...

Appendix B: PC Serial Ports
Workarounds and Solutions to the
IRQ Conflict Problem
It is important to remember that the IRQ conflict is a problem in hardware; it
cannot be resolved in software alone. Consequently, there are only three
alternatives for working around or resolving it:
Workaround 1: Configure your serial devices such that you use only two
at any one time, and those two use serial ports with unique IRQs.
This is the simplest workaround to the IRQ conflict problem, but it does not
solve the...