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OVERVIEW OVERVIEW ________
FEATURES FEATURES ________
The LiteComm-TP Toolbox(tm) is a set of powerful routines
designed to provide easy access to the full capabilities of
the PC's asynchronous communications ports. In its initial
release, the LiteComm-TP ToolBox supports fully interrupt-
driven and buffered communications support on COM1 thru COM4
simultaneously. Now you can quickly incorporate
sophisticated communications support in your applications
without having in-depth knowledge of how the hardware
functions.
LiteComm-TP is implemented as a set of 3 units for the basic
product, with additional units providing the protocol-engine
capability. The protocol engines are a part of the
registered version of the package.
The LiteComm ToolBox was originally developed in the C
language for use in CAD/CAM applications that required the
ability to have PC compatible systems communicating with a
variety of devices. The introduction of version 4.0 of
Turbo PASCAL1 has made it possible for use to extend the
power and flexibility of the original LiteComm ToolBox(tm)
to Turbo PASCAL programmers.
THE SHAREWARE CONCEPT THE SHAREWARE CONCEPT _____________________
Shareware is a "try before you buy" means of software
distribution. If you find a shareware product useful, pay
the registration fee, and let the authors know that you
support their efforts.
Information Technology, Ltd., is a member of, and supports
the standards of, ASP, The Association of Shareware
Professionals.
____________________
1 Turbo PASCAL is a registerd trademark of Borland
International
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
LICENSE, WARRANTY AND REGISTRATION LICENSE, WARRANTY AND REGISTRATION __________________________________
LICENSE LICENSE _______
The LiteComm-TP ToolBox, is distributed as a shareware
product. In its shareware form, support is limited to COM1
only. To receive the units that support the extended
features of LiteComm-TP and/or the source code for the
product, register your copy today. See the registration form
at the end of this manual.
Information Technology, Ltd, grants to registered users a
non-exclusive, perpetual license to the LiteComm-TP ToolBox,
subject to these terms and conditions:
1. You must treat your copy of the LiteComm-TP
Toolbox as you would a book. You may install
the LiteComm-TP ToolBox on more than one
machine, but you may use only one copy at a
time. If you desire, site licenses are
available at a reduced cost. You may make as
many copies of the LiteComm-TP ToolBox as you
require for the sole purpose of backup.
2. You may incorporate portions of the LiteComm-TP
ToolBox in products that you develop without the
payment of additional royalties or license fees.
You must include the statement 'Portions
Copyright 1987, 1988, Information Technology,
Ltd' in your product's documentation.
3. You may copy and redistribute the shareware
portion of the LiteComm-TP ToolBox, commonly
known as LCOMMTP.ARC, but you may not modify in
any way, the contents of the shareware package.
Further, you may not charge a fee for providing
such a copy, beyond a maximum $4.00 copying or
duplication fee, without the express, written
consent of Information Technology, Ltd,
4. You may not redistribute, in any form, the
source code for the LiteComm-TP ToolBox.
Further, you may not translate the source code
for the LiteComm-TP ToolBox into any other
language without the express, written consent of
Information Technology, Ltd.
Page 2
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
5. Information Technology reserves the right to
change both the LiteComm-TP ToolBox or its
documentation without prior notice, with no
obligation to you, the licensee.
Page 3
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
6. You agree that any disputes arising from this
license will be subject to the laws of the state
of Rhode Island.
7. You agree to hold the developer and distributors
of the LiteComm-TP ToolBox harmless for any
damages, either direct or consequential, that
might arise from the use of this product.
8. You acknowledge that the LiteComm-TP ToolBox,
libraries, source code, and documentation are
the copyrighted property of Information
Technology, Ltd.
9. By your use of the LiteComm-TP ToolBox, you
acknowledge that you have read, and understand
the terms and conditions of this license.
WARRANTY WARRANTY ________
The LiteComm-TP ToolBox is distributed as-is and without
warranty, including, but not limited to, the implied
warranties of merchantability and fitness for a particular
purpose.
Information Technology, Ltd does warrant the distribution
media for a period of 30 days. During that period,
Information Technology, Ltd will replace the distribution
media or provide a refund at its option.
Page 4
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
REGISTERING YOUR COPY REGISTERING YOUR COPY _____________________
Registration of your copy of the LiteComm-TP ToolBox
provides you with several benefits:
1. Puts you on our mailing list for low-cost
updates, enhancements, and alert bulletins when
they occur.
2. Gives you access to telephone support. Sorry,
but we cannot provide support by telephone to
unregistered user's of the ToolBox. Unregistered
users can leave EMAIL on Compuserve to
70166,1152; on GEnie to I.TECH; and on DELPHI to
RBMACE. We will respond to EMAIL on an as-
available basis.
3.Helps to further the shareware concept.
To register your copy, use the form at the end of this
documentation. You may also register on-line through
Compuserve, GEnie, or DELPHI, using EMAIL.
Page 5
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
NOTE NOTE ____
LiteComm-TP is a package undergoing continuing development.
Registered users of the product receive, in addition to the
fully-functional base package, units that provide protocol
engines supporting XModem, and YModem protocols.
We plan to follow these with similar engines for Windowed
XModem CompuServe B, Telink, and other protocols. These
engines, as they are released, will only be made available
to registered ToolBox users. The shareware version, as
enhanced but without the protocol engines, will continue to
be offered.
Page 6
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
COMMUNICATIONS AND THE PC COMMUNICATIONS AND THE PC _________________________
PC SHORTCOMINGS PC SHORTCOMINGS _______________
This section is intended as a mini-tutorial on ______________________________________________
communications concepts. We encourage you to read it, _____________________________________________________
although it is not strictly necessary to do so. _______________________________________________
The IBM-PC, and its close compatibles, is a generally well
thought-out, flexible, and well-executed computer.
Unfortunately, not as much can be said for the thought which
was given to the software which is meant to provide access
to that hardware. One of the shortcomings which is most
noticeable is in the support, or rather lack of it, that is
provided to handle access to the serial port. Support for
the serial port is limited by the BIOS to polled mode only,
i.e. a program must interrogate the port on a regular basis
to avoid losing received characters, and to check to
determine whether or not the port is ready to send a
character. Not only is this mode of operation primitive; it
also tends to cause complications when attempting to perform
any but the simplest of tasks, at slow speeds.
A novice might think that the hardware, in some way, is the
limiting factor. In fact, everything that is needed,
hardware-wise, to support a more sophisticated method of
handling the serial port is already there. All that is
missing is the software follow-through. The LiteComm-TP
ToolBox provides this missing software.
THE 8250 UART THE 8250 UART _____________
The term serial port comes from the fact that both incoming
and outgoing characters entering and leaving the port do so
in a bitwise fashion. When we send a character out the
serial port, the responsible circuitry sends out information
one bit at a time. When we receive a character, this
circuitry accepts the individual bits and reassembles them
into a recognizable character. These very complex operations
are performed automatically by the 8250 UART (Universal
Asynchronous Receiver-Transmitter).
Page 7
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
The 8250 UART is a fully programmable device that permits
independent control of the various parameters that affect
serial communications, i.e. baud rate, parity, number of
data bits, and number of stop bits. The 8250 also optionally
supports four types of interrupts, error/break detection,
modem status change detection, transmitter ready, and
received character ready. The LiteComm-TP ToolBox fully
supports all four type of interrupts.
The term asynchronous implies that there is no absolute asynchronous ____________
timing associated with the transmission of information.
Instead, the clocking-in of the data bits is done by clocking-in ___________
counting the bits. The first bit sent or received is call
the start bit and signals the beginning of a new character.
The individual data bits follow the start bit which are
clocked out and in at the specified data rate, with the
least significant bit transferred first and the parity bit,
if present, transferred last. Finally one or more stop bits
follow, signalling the end of the character.
Page 8
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
The 8250 UART takes care of all of the mechanics associated
with the process described in the preceding paragraph. The
UART will also detect and report error which may occur in
the process. For example, if the parity bit is incorrect,
the UART reports the fact. If too few or too many bits are
received, the UART will report a framing error or overrun
error respectively.
Since the transmission of information may depend on complex
interactions with another device, such as a modem or
computer, the 8250 can also report on the status of the
handshaking lines used to provide information about the handshaking ___________
status of the connection with the other device. These
signals are explained below.
SIGNAL DESCRIPTIONS
_______________________________________________________________
| |
CTS Clear To Send The other device will | |
accept a transmission. | |
DSR Data Set Ready The other device | |
is enabled. | |
RI Ring Indicator Usually reserved | |
for modems only. The | |
phone is ringing | |
DCD Carrier Detect Usually reserved for | |
modems. The other modem's | |
carrier signal was | |
detected. | |
_______________________________________________________________ | |
The header file for the LiteComm-TP ToolBox contains the
various bit masks required for you to make use of the
information provided by the 8250 UART.
TOOLBOX NOTES AND WARNINGS TOOLBOX NOTES AND WARNINGS __________________________
Before you can send or receive information on a serial port
using the ToolBox, you must use the open function to enable
the line. This function initializes the 8250 UART with the
correct parameters, and introduces the UART into the
interrupt structure of the PC. The ToolBox will detect, and
report, any errors that you may make in selecting the port
or specifying the initial parameters. The ToolBox cannot and
will not detect an attempt to open a non-existent serial
port.
Page 9
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
The ToolBox interfaces directly with the interrupt structure
of the PC. It is critical that, before exiting a program
that has opened a serial port that the serial port is closed
with the close function. If you exit your program without
closing the port, you may cause your system to crash since
the interrupt vector for the port might point to a section
of memory that no longer contains the needed code to support
the interrupt. As an alternative, Turbo PASCAL permits you
to install one or more exit handlers (see the PASCAL
reference). You may use this approach to provide a safe
shutdown, but be follow carefully Borland's recommendations
about implementing exit handlers.
Failure of the open function can be the result of either
improper parameters to the open function, or insufficient
memory available to allocate the requested buffers and
related control structures for the port. Memory for the
transmit and receive buffers as well as the port control
block are allocated from the heap. It is your responsibility
to insure that adequate memory is available for this
purpose.
Unless you are very familiar with the interrupt structure of
the PC, do not attempt to manipulate the interrupt enable
flag outside of the ToolBox. The ToolBox sets and clears the
interrupt enable flag at appropriate times and assumes that
it has sole control over the flag.
Unless otherwise specified, all library functions have been
compiled with the default structure alignment, i.e. the
structure alignment switch has not been used in creating the
ToolBox library.
LITECOMM-TP HISTORY LITECOMM-TP HISTORY ___________________
VERSION 1.0 VERSION 1.0 ___________
Version 1.0 is the first version of LiteComm-TP to be
offered to the general public, although there have been 2
Beta releases prior to Version 1.0 release. Version 1.0 is
the functional equivalent of the original LiteComm ToolBox,
version 2.5, except for YModem support which is still
undergoing development for the C environment.
Page 10
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
BEYOND COM2 BEYOND COM2 ___________
THE TOOLBOX METHODOLOGY THE TOOLBOX METHODOLOGY _______________________
In the design of the original PC, and in subsequent
variations such as the PC/AT, there were only provision for
two serial ports. Many manufacturers of add-in products,
both serial ports and internal modems have added the
capability to support 1 or more additional ports beyond the
COM2 limit. Generally, this can cause problems in the PC
since there is no room in the interrupt request scheme for
additional levels of interrupts, and there are no designated
interrupt vector for other additional ports.
The ToolBox approach to resolving these issues is to permit
the programmer a degree of control over the parameters that
govern the interrupt mechanism for COM3 and COM4.
Specifically, these parameters are: 1) the interrupt request
(IRQ) bit that is used to mask the 8259 interrupt
controller; 2) the interrupt vector number (not address) to
which the port is attached; and 3) the base i/o register for
the port itself. Of course, it is assumed that the port is
based upon the 8250 UART or compatible device.
Before you attempt to use COM3 and/or COM4, you must
determine from the port's documentation, the appropriate
values for these three parameters. As distributed, the
ToolBox assumes the following:
COM3 COM4 ____ ____
IRQ Bit 4 3
Vector # 0Ch 0Bh
Base Reg 3E8h 2E8h
You may change any or all of these values by using the
PortChange function described below, but only before you
open the port with CommOpen. Once the port has been opened,
PortChange is ineffective, and PortChange will not work on
COM1 or COM2.
CAUTIONS CAUTIONS ________
Page 11
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
There is an intimate relationship between the IRQ setting
and the interrupt vector to which it relates. In the PC,
this relationship is controlled, in part, by the 8259
interrupt controller that is set during BIOS initialization.
In brief, the BIOS settings for the PC (and most close
compatibles) establish IRQ0 as being vector number 08h, and
subsequent IRQ levels at increasing vector numbers. These
vector numbers (or types in INTEL terms) act as a cpu-
directed call table to locations in the lowest 1K of system
memory. We can alter how the system responds to a given
interrupt by replacing or changing the values in the
associated vector position to point to a routine which we
supply.
COM3 and COM4 share two critical parameters with COM1 and
COM2 respectively, the IRQ bit and the interrupt vector
number. If you intend to use COM1 with COM3 or COM2 with
COM4 simultaneously, you must change the BOTH the vector
number and the IRQ for COM3 or COM4 to an unused or un-
needed vector. The ability for your add-on ports to handle
such a change is highly hardware dependent, so check your
port's documentation carefully. Failure to do so will result
in loss of data at best, and a system lockup at worst.
Judging from the questions asked by some users of LiteComm-
TP, there is evidently some mis-understanding about using
ports beyond COM2, and how this all relates to your
hardware. Before you can successfully use COM3 or COM4, you
must consider the following:
1. Does the hardware permit a change to the base
port and/or the interrupt vector to which the
port responds. Some expansion cards will
support changing one and not the other, giving
rise to potential hardware conflicts and lost
data.
2. Does the hardware permit re-assignment of the
IRQ priority. Some expansion cards permit you to
alter the IRQ priority, some won't. Suffice it
to say from the previous discussion the any
change to the IRQ priority must allow a
corresponding change to the interrupt vector
number. Without this capability, reprogramming
of the 8259 chip would be required.
Page 12
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
3. In fact, many add-on cards permit this dual
change simply by making a single switch or
jumper setting. Unfortunately, the documentation
for these cards generally assume that you are
aware of the dual nature of the IRQ vector
relationship, and may leave you with the
impression that you are changing one and not the
other. In most circumstances, this is not the
case.
The point to all of this is that LiteComm-TP can only
provide as much support as the hardware permits, or is
capable of responding to. If you wish to use other than the
default base port, interrupt vector, or irq priority for
COM3 or COM4, then your expansion card must be capable of
supporting the new values; in other words, these values are
all hardware-provided, and are recognized by the LiteComm-TP
software. If your hardware does not permit changing a value,
LiteComm-TP cannot improve the situation.
We should, at this point, add one final caution about how
interrupt priorities function, and their relationship to the
irq bit the you may select. The standard PC permits 8
interrupt priority levels, with the programmable timer
having the highest priority, and the parallel printer port
having the lowest priority. When an interrupt occurs, the
interrupt controller (8259 chip) masks out all other
interrupts from the priority of the interrupting device and
all lower priority devices.
As an aid to making COM3 and COM4 "fit", LiteComm-TP
supports interrupt chaining for the COM3 and COM4 ports. If
you use COM3 or COM4, when an interrupt occurs, the kernel
will attempt to determine if the interrupt was caused by the
supported port or from some other source.
If the kernel determines that the supported port did not
cause the interrupt, an automatic chain to the original
interrupt handler for that interrupt level (IRQ level) will
take place, allowing you to "patch in" or share the
available interrupt vectors.
If you intend to use other than the provided defaults, be
sure that you understand the interrupt mechanism. The use of
the automatic chaining described above can be particularly
troublesome under some circumstances, resulting in loss of
interrupts and, potentially, a system crash.
Page 13
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
PACKAGE CONTENTS PACKAGE CONTENTS ________________
Your distribution diskette contains several files that are
important to you. All distribution diskettes, at a minimum,
include the following files in the diskette's root
directory:
.fo off
PSERIAL.NUM SERIAL NUMBER OF THIS COPY
READ.ME LATEST INFORMATION ABOUT
LITECOMM-TP
LTCOMM.ARC SHAREWARE VERSION AND DOCUMENTATION
FILES
LTUNITS.ARC FULLY FUNCTIONAL UNIT FILES
If you registered for the source code modules, the diskette
contains a sub directory called SOURCE. The SOURCE
directory contains 2 source code archives.
LITECOMM-TP SOURCE CODE LTSRC.ARC
XMODEM ENGINE SOURCE CODE LTXMSRC.ARC
Page 14
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
INSTALLATION INSTRUCTIONS INSTALLATION INSTRUCTIONS _________________________
In the following discussion, we assume that your regular ________________________________________________________
unit files are contained in a directory called \TP. \TP ___________________________________________________
To install the unit files used with LiteComm-TP, perform the
following steps:
1. CD \TP
2. ARC E A:LTUNITS
Since Turbo PASCAL permits you the flexibility of having a
separate sub-directory for units, you should execute the
above instructions in whatever directory you use for units.
If you are installing only the units, this completes the
installation procedure. If you have registered for the
package's source code, we recommend that you create a
separate sub-directory. The example below assumes that you
will use a directory named COMM to hold the LiteComm-TP and
XModem source code modules. To install the LiteComm-TP
source code, do the following:
1. MD \COMM
2. CD \COMM
3. ARC E A:LTSRC *.*
4. ARC E A:LTXMSRC *.*
We strongly urge that you use the recommended approach in
handling the source code to avoid naming conflicts that
might arise.
GENERAL NOTES GENERAL NOTES _____________
Page 15
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
In the discussion of the various functions which follow, you
should assume that any references to the 'port' variable
refer to a variable or constant that may take on a value of
from 1 to 4. No other values are acceptable, and will be
rejected.
While we feel that LiteComm-TP is written in the most
efficient way possible, commensurate with good programming
practice, we cannot be responsible for variations caused by
hardware configurations or other factors beyond our control.
LiteComm-TP has been tested, and is known to perform on, the
IBM PC-AT and several compatible systems such as the Zenith
and Wyse equivalents. LiteComm-TP has not been tested in
environments in which other software, most significantly TSR
(terminate and stay resident) modules exist. Some TSR
programs that "steal" interrupts for their own purposes
present an unfavorable environment to other programs that
rely on the interrupt structure of the computer.
Should you experience erratic behavior with LiteComm-TP in a
TSR-type situation, try executing your application without
the TSR module being present. If the problems you have
experienced disappear, suspect the TSR module.
Conversely, LiteComm-TP provides an excellent vehicle for
supporting TSR programs that you may write. Since the
package is fully reentrant, your only concern need be with
those aspects of TSR programs are of normal concern, e.g.
the non-reentrant nature of DOS. LiteComm-TP never uses DOS
functions and may therefore be safely used in a TSR
environment.
Page 16
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
PROCEDURE AND FUNCTION REFERENCE PROCEDURE AND FUNCTION REFERENCE ________________________________
In the following pages, we provide the detailed information
about each of the available LiteComm-TP ToolBox functions
and procedures. Each definition includes, at a minimum, a
summary of how the function or procedure is referenced, in
which unit the function or procedure is found, a description
of what the function or procedure does, and an indication of
those values, if any, that might be returned.
Where appropriate, we include additional documentation about
the function. Some definitions include examples, in the
sense of code fragments illustrating the function's usage.
More importantly, some definitions include additional notes
and warnings as well as references to other functions within
the package.
We have made every effort to insure that the documentation
of the functions is complete and accurate. The style and
manner of the documentation assumes that the reader is
thoroughly familiar with the elements of C syntax and common
conventions.
UNIT USAGE UNIT USAGE __________
To assist you in developing your own applications, you will
need to know the following information.
Unit Uses
LctKrnl DOS
LctSupp DOS, LctKrnl
LctHayes DOS, LctSupp
LcTimer DOS *
LTXMKrnl DOS, LctSupp, LcTimer *
LTXModem DOS, LctSupp, LTXMKrnl
LcTimer *
* This unit part of registered version only.
Page 17
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
PortChange function LctKrnl PortChange function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Changes one or more of the critical parameters for port COM3
or COM4.
DECLARATION DECLARATION ___________
Portchange(CPort:integer; NewBase:word; NewIrq,
NewVector:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
This function must be used before the port is opened to be
effective. To leave any of the parameters at its default
value, make the corresponding entry 0. Note that vector is a
vector number, not an address or pointer.
The irq parameter should not be taken to be the irq
(interrupt request number), but rather the irq mask. For
example, the correct value for irq4 is NOT 4, but a byte in
which bit 4, using INTEL's bit numbering, is set to a value
of 1. Thus, to use irq priority 4 as the irq for either COM3
or COM4, you would specify $10 as the value of irq when
calling PortChange.
If you intend to change the default irq settings, you MUST
also make a corresponding change to the vector number. See
the preceding section about using COM3 and COM4 for
additional details. Failure to follow this rule may make the
port appear to be non-functional.
The PortChange function does NOT check to determine that you
have provided both an IRQ mask AND a new vector number.
Page 18
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
PortChange returns a value of TRUE if the change was
successful, false otherwise.
Page 19
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
EXAMPLE EXAMPLE _______
Var
Newbase : word;
Newirq : byte;
NewVector : byte;
Begin
Newbase := $03E8;
Newirq := $10;
NewVector := $0C;
if PortChange(3, Newbase, Newirq, NewVector)
then
Writeln('Port 3 Changed')
else
Writeln('Error changing Port 3');
end;
Page 20
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
CommOpen function LctKrnl CommOpen function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Prepares the specified port for use by the other functions
DECLARATION DECLARATION ___________
CommOpen(CPort, Baud:integer; Parity:char; Databits,
Stopbits, InSize, OutSize:integer)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Opens the specified port for use and attaches an interrupt
handler to DOS for the port. The function allocates buffers
for input and output of the specified sizes, and sets the
port to the parameters specified. The minimum value for
InSize is 128; the minimum size for OutSize is 64. A port
opened in this manner must be closed using CommClose before
program termination to avoid the possibility of a system
crash.
The parameters passed to the function are discrete values,
and must be drawn from the following lists:
Baud: 110, 300, 600, 1200, 2400, 4800, 9600, 19200
Parity: E, O, N, M, S
E - Even
O - Odd
N - None
M - Mark
S - Space
Databits: 5, 6, 7, 8
StopBits: 1, 2
Page 21
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
A return of TRUE indicates the port has been successfully
opened and is ready for use. A return of FALSE indicates an
error occurred, either as the result of an invalid
parameter, or insufficient heap space available to allocate
the buffers and control structures for the port.
Page 22
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
EXAMPLE EXAMPLE _______
Var
Baud, Databits, Stopbits : integer;
Parity : char;
Insize, Outsize : integer;
begin
Baud := 2400;
Parity := 'E';
Databits := 7;
Stopbits := 1;
Insize := 256;
Outsize := 256;
if CommOpen(1, Baud, Parity, Databits,
Stopbits, Insize, Outsize) then
Writeln('COM1 available for use')
else
Writeln('Error opening COM1');
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for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
CommClose procedure LctKrnl CommClose procedure LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Closes a port that has been opened by the CommOpen function
DECLARATION DECLARATION ___________
CommClose(CPort:integer)
REMARKS REMARKS _______
This function is the companion to CommOpen and, in effect,
performs the opposite action. CommClose detaches the kernel
interrupt handler from the port, and reconnects the previous
interrupt handler. CommClose also release dynamically
allocated memory used for buffering and control structures.
Failure to call CommClose before terminating a program may
result in unexplained system crashes or hangs.
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_______________________________________________________________ _______________________________________________________________
CommSetup function LctKrnl CommSetup function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Provides the capability of changing the parameters for an
open port, without breaking the connection or closing the
port.
DECLARATION DECLARATION ___________
CommSetup(CPort, Baud:integer; Parity:char; Databits,
Stopbits:integer)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
The CommSetup function is a subset of the CommOpen function
and the remarks made in the description of CommOpen apply.
This function is useful if you wish to change the basic
communication parameters of the specified port that has
already been opened without CommClose'ing the port and
breaking the connection.
SEE ALSO SEE ALSO ________
CommOpen
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for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
ValidatePort function LctKrnl ValidatePort function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Verifies that the specified port has been opened and returns
a pointer to the Communications Control Block for the port.
DECLARATION DECLARATION ___________
ValidatePort(CPort:integer)
RESULT TYPE RESULT TYPE ___________
CCBPTR
REMARKS REMARKS _______
Used internally to validate that the port number specified
is correct and has been opened with the CommOpen function.
May be of use to you in writing certain applications that
require access to the Communications Control Block. The
function returns a value of NIL if the specified port is
incorrect or not open.
EXAMPLE EXAMPLE _______
if ValidatePort(2) <> NIL then
Writeln('The port has been opened')
else
Writeln('The port is nor presently open');
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for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
BytesInInput function LctSupp BytesInInput function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Returns the number of characters currently available in the
input buffer (BytesInInput) or the number of untransmitted
characters in the output buffer (ByteInOutput).
DECLARATION DECLARATION ___________
BytesInInput(CPort:integer)
BytesInOutput(CPort:integer)
RESULT TYPE RESULT TYPE ___________
integer
REMARKS REMARKS _______
May be used to determine the number of characters currently
in the input (BytesInInput) or output (BytesInOutput)
buffers for the port. In the event of an error (bad port), a
value of -1 is returned.
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_______________________________________________________________ _______________________________________________________________
ModemStatus function LctKrnl ModemStatus function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Returns the last know status of the modem control lines for
the specified port.
DECLARATION DECLARATION ___________
ModemStatus(CPort:integer)
RESULT TYPE RESULT TYPE ___________
byte
REMARKS REMARKS _______
Use this function to determine the last known state of the
modem-supplied handshake signals. These may be tested using
the values included in the unit, using PASCAL's bitwise AND
operator. NOTE: You should be aware that the handshake
signals returned are reset once this function is called.
Subsequent calls to this function will return to last known
value for all signals. The signals which are tracked are
CTS, DSR, RI, and DCD.
To determine which signals, if any, have changed use the
DeltaXXX bits returned. For example, if CTS has changed, the
DeltaCTS bit will be set. The actual CTS value (on or off)
will be found in the CTS bit of the returned byte.
In the event of an error, a byte of $00 is returned.
EXAMPLE EXAMPLE _______
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Var
CStat : byte;
begin
CStat := ModemStatus(1);
if CStat and DeltaCTS = DeltaCTS then
if CStat and CTS <> CTS then
Writeln('The connection is broken');
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for Microsoft, Datalight and Turbo C
_______________________________________________________________ _______________________________________________________________
ErrorStatus function LctKrnl ErrorStatus function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Return the last known error status for the specified port.
DECLARATION DECLARATION ___________
ErrorStatus(CPort:integer)
RESULT TYPE RESULT TYPE ___________
byte
REMARKS REMARKS _______
Returns the last known state of the serial port's error
status bits, encoded in a byte. These may be tested using
the constants defined in the unit in conjunction with
PASCAL's bitwise AND operator. The applicable values that
may be checked are OverRun, BadParity, BadFrame, and
BreakDet. In the event of an error, a byte of $00 is
returned.
Once the error status bits have been read in this fashion,
they are reset to $00, and will remain so until the next
error occurs. Since this process happens asynchronously, it
is not possible for your application to determine which
character created the error, only that the error occurred.
EXAMPLE EXAMPLE _______
Var
EStat : byte;
begin
EStat := ErrorStatus(2);
if EStat and BreakDet = BreakDet then
Writeln('Break Signal detected on Port 2');
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_______________________________________________________________ _______________________________________________________________
SetModemSignals function LctKrnl SetModemSignals function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Allows the programmer to set the individual modem control
lines for the specified port.
DECLARATION DECLARATION ___________
SetModemSignals(CPort:integer; NewSet:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Set one or more of the modem control signals. Because of the
need to always have OUT2 set for interrupt support, the
function always provides the correct setting for this bit.
The value of NewSet is bitwise OR'ed with the current set of
values to produce a new modem control setting. The value of
NewSet DOES NOT replace the current values. Use the
constants supplied in the unit to obtain the correct values.
These include DTR and RTS.
EXAMPLE EXAMPLE _______
begin
if SetModemSignals(1, (DTR and RTS)) then
Writeln('Port is ready to transmit')
else
Writeln('Unable to set modem signals');
SEE ALSO SEE ALSO ________
ClearModemSignals, FlipModemSignals
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_______________________________________________________________ _______________________________________________________________
ClearModemSignals function LctKrnl ClearModemSignals function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Allows the programmer to clear (reset) the individual modem
control lines for the specified port.
DECLARATION DECLARATION ___________
ClearModemSignals(CPort:integer; NewSet:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Clears (resets) one or more of the modem control signals.
Because of the need to always have OUT2 set for interrupt
support, the function always provides the correct setting
for this bit.
The compliment of NewSet is bitwise AND'ed with the current
set of values to produce a new modem control setting. The
value of NewSet DOES NOT replace the current values. Use the
constants supplied in the unit to obtain the correct values.
These include DTR and RTS.
EXAMPLE EXAMPLE _______
begin
if ClearModemSignals(1, RTS) then
Writeln('RTS for Port 1 has been dropped')
else
Writeln('Unable to clear RTS');
SEE ALSO SEE ALSO ________
SetModemSignals, FlipModemSignals
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_______________________________________________________________ _______________________________________________________________
FlipModemSignals function LctKrnl FlipModemSignals function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Allows the programmer to compliment(toggle) the individual
modem control lines for the specified port.
DECLARATION DECLARATION ___________
FlipModemSignals(CPort:integer; NewSet:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Complements(toggles) one or more of the modem control
signals. Because of the need to always have OUT2 set for
interrupt support, the function always provides the correct
setting for this bit.
The value of NewSet is bitwise XOR'ed with the current set
of values to produce a new modem control setting. The value
of NewSet DOES NOT replace the current values. Use the
constants supplied in the unit to obtain the correct values.
These include DTR and RTS.
EXAMPLE EXAMPLE _______
begin
if FlipModemSignals(1, RTS) then
Writeln('RTS for Port 1 has been changed')
else
Writeln('Unable to change RTS');
SEE ALSO SEE ALSO ________
SetModemSignals, ClearModemSignals
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_______________________________________________________________ _______________________________________________________________
EnableXon function LctKrnl EnableXon function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Enable or disable the semi-automatic flow control features
of LiteComm-TP
DECLARATION DECLARATION ___________
EnableXon(CPort:integer; XonFlag:boolean)
RESULT TYPE RESULT TYPE ___________
boolean;
DESCRIPTION DESCRIPTION ___________
If XonFlag is TRUE, turns on semi-automatic XON-XOFF flow
control function. If XonFlag is FALSE (the default setting),
automatic flow control is disabled. When enabled, the kernel
will automatically transmit an XOFF if and when the input
buffer is approximately 2/3 full and will automatically
recognize an XOFF sent by the companion system. If the
companion system transmits an XOFF, the kernel will refuse
to send any characters until the condition is cleared.
It is the programmer's responsibility to transmit XON when
conditions permit. See the XoffSent function to tell if an
automatic XOFF has been sent by the kernel. See the XoffRecd
function to determine if the kernel has detected an XOFF.
If you intended to implement a protocol that might include
the XON-XOFF characters, be sure to disable the automatic
flow control. Failure to do so may result in a system hang.
SEE ALSO SEE ALSO ________
XoffRecd, XoffRecd
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_______________________________________________________________ _______________________________________________________________
XoffRecd function LctKrnl XoffRecd function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Reports whether or not the kernel has detected an XOFF from
the companion system
DECLARATION DECLARATION ___________
XoffRecd(CPort:integer)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Returns TRUE if an XOFF has been received, FALSE otherwise.
If an XOFF has been received, the port's flag will be reset,
and transmission to the companion system will be permitted.
If an XON is received from the companion system, the port's
flag will also be reset, permitting further transmissions to
occur. Be aware that if the companion system never sends an
XON after sending an XOFF, a possible race condition may race ____
occur, resulting in a system hang.
SEE ALSO SEE ALSO ________
EnableXon, XoffSent
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_______________________________________________________________ _______________________________________________________________
XoffSent function LctKrnl XoffSent function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Reports whether or not the kernel has automatically sent an
XOFF to the companion system.
DECLARATION DECLARATION ___________
XoffSent(CPort:integer)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Returns TRUE if the kernel has sent an XOFF to the companion
system, FALSE otherwise. If an XOFF has been sent, the
port's flag will be reset. You must send an XON character to
the companion system to permit transmissions to proceed.
SEE ALSO SEE ALSO ________
EnableXon, XoffRecd
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_______________________________________________________________ _______________________________________________________________
LctGet function LctSupp LctGet function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Returns an available character from the ports input buffer.
DECLARATION DECLARATION ___________
LctGet(CPort:integer; var Ch:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Places the next available character in the input buffer for
the port in Ch. The function returns a value of TRUE if
there is a character available, FALSE if there is no
character available or on an error. The contents of Ch are
undefined when the return is FALSE.
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_______________________________________________________________ _______________________________________________________________
LctPeek function LctSupp LctPeek function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Permits you to look at the next character in the ports input
buffer without removing if from the buffer.
DECLARATION DECLARATION ___________
LctPeek(CPort:integer; var Ch:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Places the next available character in the input buffer for
the specified port into the Ch variable, but does not remove
the character from the buffer. This allows the application
to look-ahead by one character in a non-destructive fashion. look-ahead __________
Returns FALSE if the port is not active, or if there are no
characters in the port's buffer, TRUE otherwise. The
contents of Ch are undefined when the result is FALSE
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_______________________________________________________________ _______________________________________________________________
LctPut function LctSupp LctPut function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Places a character in the port's transmit buffer to be sent
when the port is ready.
DECLARATION DECLARATION ___________
LctPut(CPort:integer; Ch:byte)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
Returns TRUE if successful. Note that this does not
guarantee that the character has been sent, only that no
errors were detected. Returns FALSE if the port is not
active, or if there no room in the port's buffer.
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_______________________________________________________________ _______________________________________________________________
GetStream function LctSupp GetStream function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Gets a stream of N characters from the port's
input buffer
DECLARATION DECLARATION ___________
GetStream(CPort:integer; var Buff; BCnt:integer)
RESULT TYPE RESULT TYPE ___________
integer
REMARKS REMARKS _______
Reads a stream of, at most, BCnt characters from the serial
port's input buffer into the Buff array. Returns the count
of characters actually transferred, or -1 if an error
occurs. NOTE that Buff is an array of characters or bytes,
not a string, although you may treat a string variable like
an array, as shown below.
EXAMPLE EXAMPLE _______
Type
MaxStr = string[256];
Var
StrBuff : MaxStr;
RecdLen : integer;
begin
RecdLen := GetStream(2, StrBuff[1], 256);
if RecdLen <= 0 then { error or no char }
StrBuff[0] := 0
else
StrBuff[0] := Chr(RecdLen);
end;
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_______________________________________________________________ _______________________________________________________________
PutStream function LctSupp PutStream function LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Places a stream of, at most, N characters in the port's
transmit buffer.
DECLARATION DECLARATION ___________
PutStream(CPort:integer; var Buff; BCnt:integer)
RESULT TYPE RESULT TYPE ___________
integer
REMARKS REMARKS _______
Buff is an array of character or byte, not a string,
although it is possible to specify a string variable, using
the same approach as outlined for the GetStream function.
PutStream returns the number of characters actually placed
into the buffer. Note that this does not guarantee that the
characters have been sent. A value of 0 will be returned if
any error occurs, or if there no room in the port's buffer.
SEE ALSO SEE ALSO ________
PutStream
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_______________________________________________________________ _______________________________________________________________
Buffer Flushing functions LctSupp Buffer Flushing functions LctSupp
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Provides several high level buffer management functions to
control the contents of the port's transmit and receive
buffers
DELCLARATION DELCLARATION ____________
function PurgeTxBuff(CPort:integer)
function PurgeRxBuff(CPort:integer)
procedure FlushUntilMatch(CPort:integer; Ch:byte)
procedure FlushNBytes(CPort:integer; N:integer);
RESULT TYPE RESULT TYPE ___________
boolean for PurgeTxBuff, PurgeRxBuff
REMARKS REMARKS _______
The PurgeRxBuff and PurgeTxBuff functions remove all
characters from the port's receive and transmit buffers
respectively and discard them; untransmitted characters in
the transmit buffer are NEVER sent; unprocessed characters
in the receive buffer are lost. Both functions return a
value of TRUE if no errors were encountered, FALSE
otherwise. An empty buffer is NOT considered an error.
The FlushUntilMatch procedure will continually dispose of
received characters until the character Ch is received. The
procedure will return when the character Ch is detected, or
when there are no more characters in the port's input
buffer.
The FlushNBytes procedure removes, at most, N characters
from the port's receive buffer.
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_______________________________________________________________ _______________________________________________________________
SendBreak function LctKrnl SendBreak function LctKrnl
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Send a true Break signal
DECLARATION DECLARATION ___________
SendBreak(CPort:integer)
RESULT TYPE RESULT TYPE ___________
boolean
REMARKS REMARKS _______
SendBreak generates a BREAK signal using a particular
characteristic of the 8250 UART to generate an accurate
BREAK at any baud rate. BREAKS generated in this manner are
timed based upon the baud rate at which the 8250 is
currently initialized. This function may or may not work
correctly with other than the actual 8250 UART.
Returns TRUE if successful. Returns FALSE if an error is
detected.
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_______________________________________________________________ _______________________________________________________________
HAYES MODEM FUNCTIONS LctHayes HAYES MODEM FUNCTIONS LctHayes
_______________________________________________________________ _______________________________________________________________
FUNCTION FUNCTION ________
Provides support for various aspects of modems the support
the Hayes(tm) command set.
DECLARATIONS DECLARATIONS ____________
CONST
NUMRES = 0 { numeric result codes}
WRDRES = 1 { word result codes }
SPKOFF = 0 { speaker off }
SPKON = 1 { speaker on until CD }
SPKSPC = 2 { speaker always on }
ONHK = 0 { go on-hook (hang up) }
OFFHK = 1 { go off-hook (lift receiver) }
OFFHKS = 2 { go off-hook, don't close relay }
BASIC = 0 { basic result set }
EXSET1 = 1 { extended results, set 1 }
EXSET3 = 2 { extended results, set 3 }
EXSET4 = 3 { extended results, set 4 }
TYPE
TelNumStr = string[20];
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procedure SetType(NType : byte)
procedure SetSet(NSet : byte)
function RetType : byte
function RetSet : byte
function ModemCodesOn(CPort : integer):boolean
function ModemCodesOff(CPort : integer):boolean
function ModemWordResponse(CPort : integer):boolean
function ModemDigitResponse(CPort : integer):boolean
function RepeatModemCommand(CPort : integer):boolean
function ModemSpeaker(CPort : integer; Mode : byte):boolean
function SetModemRegister(CPort, Reg, NValue : integer) :
boolean
function GetModemRegister(CPort, Reg, NValue : integer) :
boolean
function ModemHalfDuplex(CPort : integer) : boolean
function ModemFullDuplex(CPort : integer) : boolean
function ModemEchoCmd(CPort : integer) : boolean
function ModemNoEchoCmd(CPort : integer) : boolean
function ModemHookMode(CPort : integer; HMode : byte) :
boolean
function ModemCarrierOn(CPort : integer) : boolean
function ModemCarrierOff(CPort : integer) : boolean
function ModemWordResponse(CPort : integer):boolean
function ModemDigitResponse(CPort : integer):boolean
function RepeatModemCommand(CPort : integer):boolean
function ModemSpeaker(CPort : integer; Mode : byte):boolean
function SetModemRegister(CPort, Reg, NValue : integer) :
boolean
function GetModemRegister(CPort, Reg, NValue : integer) :
boolean
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function ModemHalfDuplex(CPort : integer) : boolean
function ModemFullDuplex(CPort : integer) : boolean
function ModemEchoCmd(CPort : integer) : boolean
function ModemNoEchoCmd(CPort : integer) : boolean
function ModemHookMode(CPort : integer; HMode : byte) :
boolean
function ModemCarrierOn(CPort : integer) : boolean
function ModemCarrierOff(CPort : integer) : boolean
function ModemCodeSet(CPort : integer; NewSet : byte) :
boolean
function ModemPulse(CPort : integer) : boolean
function ModemTone(CPort : integer) : boolean
function ModemDial(CPort : integer; TelNo : TelNumStr) :
boolean
REMARKS REMARKS _______
The ModemCodeSet function allows you to change the set of
codes that are returned by the modem when an action is
specified.
ModemDial instructs the modem to dial the number contained
in TelNo. Do not include the dialing (ATD) prefix, or the
trailing <CR>. These are provided by the function. You may
include non-numeric characters as the contents of TelNo are
not checked. The dialing is done in the last known, pulse or
tone, mode. If you use the MpdemPulse or ModemTone
functions, then dialing will be done in the mode that was
last correctly enabled. If you have not exercised these
functions, then dialing occurs in the modems default or
power-up mode.
The ModemHalfDuplex and ModemFullDuplex functions place the
modem into local echo and remote echo modes respectively.
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The GetModemRegister function requests that the modem return
the current value of S-register Reg. Reg must be in the
range 0 to 13. Use the GetStream, or similar function, to
retrieve the modem's response. Specifying a register outside
the 0 to 13 range will cause a return of FALSE.
SetModemRegister is the companion to GetModemRegister, with
the same restrictions. Sets the S-register Reg to the value
contained in NValue. If NValue contains -1, then the
register is reset to its default (power-up) value. The
function checks the value to be certain that it is within
the limits specified for the particular register, and
returns a value of FALSE if the value is outside the
predefined limits.
ModemCarrierOff enables modem carrier detect, but disables
the modems carrier signal. The ModemCarrierOn companion
enables both carrier detect and the modems carrier signal.
When ModemCarrierOff is used the modem will receive data but
will be unable to send data.
The ModemNoEchoCmd and ModemEchoCmd functions determine
whether commands sent to the modem are echoed back to the
sending program. With echo turned off, the modem will
continue to accept commands, but will not try to redisplay
the command's characters.
ModemHookMode allows you to control the current status of
the modem's telephone line connection. See your modem's
documentation and the above constants for additional
information.
The ModemRepeatCommand function instructs the modem to
repeat the last command sequence executed. Generally, this
function is of greatest value in re-dialing numbers that are
busy, although its use is not restricted to that.
The way in which your modem responds to commands is
determined, in part, by the ModemWordResponse and
ModemDigitResponse functions. If you call ModemWordResponse,
then modem responses use the English language response
codes, e.g. CONNECT or OK. Calling ModemDigitResponse
instructs the modem to respond with code numbers only from
the currently selected response set, see the ModemCodeSet
function above.
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You may use the functions ModemCodesOn and ModemCodesOff to
specify whether you want your modem to send back response
codes when it receives a command string. In a sense, these
act as companions to the EchoCmd functions above.
Use the ModemSpeaker function to control the modem's
internal speaker, if it has one. See the above constants for
the applicable codes.
The RetSet and RetType functions return, respectively, the
last known command set (ModemCodeSet) and last known result
type (ModemWordResponse, ModemDigitResponse). The RetSet and
RetType functions are only of value when used in
conjunction with the companion functions.
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GENERAL REMARKS GENERAL REMARKS _______________
Several considerations are in order if you intend to use the
Hayes ToolBox functions.
1. You are responsible for checking the return
codes from the modem once you have given modem a
command. To make the task easier, we suggest
that you turn OFF command echo (so that you
don't have to worry about separating commands
from responses) and turn ON numeric responses
(to make the interpretation of result codes
easier and faster).
2. Be sure that you allow adequate time between
commands for the modem to process the command
and respond. Failure to observe this rule may
result in commands being misinterpreted or
"lost". You can monitor the number of characters
in the receive buffer to help you with the
timing. Or alternatively, check the response
after each command. The latter approach is more
in line with what we believe to be good
programming practice.
RETURN VALUES RETURN VALUES _____________
All functions return a value of FALSE if a port or other
error is detected, TRUE otherwise.
Page 49
CopyRight (c) 1988 Information Technology, Ltd.
LITECOMM-TP (tm) COMMUNICATIONS TOOLBOX
for Microsoft, Datalight and Turbo C
Page 50
CopyRight (c) 1988 Information Technology, Ltd.
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