Category : Communication (modem) tools and utilities
Archive   : SP144MAN.ZIP
Filename : THREE.TXT

SPORTSTER 14,400
CHAPTER 3. QUICK START

This chapter provides an overview of
basic modem settings and is designed to
quickly get you started using your
Sportster 14,400.
ù If you're already familiar with
dial-up modems, you may want to
skip ahead to the Recommended
Settings section later in this
chapter. There you'll find sugges
tions to help you make the best use
of the Sportster 14,400.
ù If you're a new modem user, the
next few sections provide some
general useful information on
modems.
Both new and experienced users may want
to refer to Chapters 4 through 7, as
well as the Glossary and Index, for
detailed information on each modem
feature as well as the terms and
concepts discussed here.

BASIC OPERATING REQUIREMENTS

For successful data communications to
occur, your communications software and
modem require that you set some minimal
parameters.

Software Parameters

Your communications program requires the
following parameters.
ù The computer or terminal serial
port to which you've attached the
modem
ù The data rate between the computer
and modem_also referred to as
serial port rate_in bits per second
ù Parity_usually None or Even
ù The number of Stop bits_the final
bit(s) attached to a data character
before transmission
ù Word length_the number of bits in a
data character without parity,
Start and Stop bits
When the modem receives an AT command
issued from the keyboard or software,
it detects the serial port rate and
data format and uses them as its
operating parameters. The remote
system must use the same word length,
parity and number of Stop bits. If you
don't know what the remote system re
quires, phone to find out before trying
to connect via modem.

Modem Parameters

The modem is shipped ready to dial out
and connect with other modems except
for Transmit Data flow control. Don't
try to make a high-speed call without
first setting the modem for this
function. See the Recommended Settings
and Alternative Settings sections later
in this chapter.

Setting Modem Parameters

To change the modem's settings, load
your communications software and follow
the procedures your software specifies
to reconfigure the modem. Various
programs may require that you do one of
the following.
ù Insert modem settings in each Dial
command string in the program's
Dialing or Phone Directory.
ù Create a modem setup string of
commands.
ù Send commands directly to the modem
(if your program displays a cursor
on a Terminal screen).
The following is an example of modem
parameter settings.
AT &H1 &B1
The &H1 command tells the modem to use
hardware flow control, and &B1 fixes
the serial port rate at the rate of the
last AT command.

RATE SHIFTING

The modem has two interfaces at which
it transmits and receives data: the
serial port interface, which it shares
with the computer or terminal, and the
phone line interface.

Phone Line Interface

The Sportster 14,400 and compatible
remote modems go through a connection
sequence to try to connect at the
highest possible rate. As long as your
software is set to at least 19.2K bps
and the modem has detected that rate
through an AT command, the modem is
always able to connect at 14.4K bps.
If the remote modem is operating at a
lower rate, your modem drops its rate
to connect and the call proceeds at the
lower rate, for example, 2400 bps.
This is called the connection rate.

Serial Port Interface

As mentioned earlier, the modem detects
its operating rate from its last
received AT command. After that, the
modem determines its serial port rate in
one of the following ways. Note that in
both cases, your software must also be
set to support the same serial port rate
option.
1.If the modem and software are set for
variable serial port rates, both the
modem and the software shift their
port rates to match any rate
switching at the phone line
interface.
If the modem connects with a remote
modem at 2400 bps, for example, you
will find after your call that your
software setting has switched down to
2400. If you want to dial out at
9600 bps, change the software setting
first, before instructing the modem
to dial.
2.If the modem and software are set for
a fixed serial port rate, the rate at
the serial port does not drop down to
match a lower connection rate. This
allows you to lock in a higher rate
at the port (for example, 38.4K or
19.2K bps) for very efficient
transmission between the modem and
the terminal.
You'll find instructions in the
following section, Recommended
Settings. If your software supports a
fixed serial port rate, you will
achieve greater throughput with this
option. Particularly if the modems
connect under data compression, a
fixed, high serial port rate can more
than triple the amount of data that
goes from one computer to the other
each second, and keep your phone line
costs to a minimum.

RECOMMENDED SETTINGS

We recommend using all of the modem's
factory settings except for flow control
and the serial port rate. Flow control
is factory-set as disabled; we recommend
that you enable hardware flow control.
The serial port rate is factory-set as
variable; we recommend that you set a
fixed, high serial port rate (as
described above). Note that to use
these recommended settings, your machine
and software must also support them.
Check the quick configuration guide that
came with the modem to see if your
communications program is listed and
what it supports. If your program is
not listed, review your software
documentation. If the software doesn't
support either hardware flow control or
a fixed rate at the computer interface,
review Alternative Settings, after this
section.
Check your software or terminal
documentation to see if your machine
supports the recommended settings.
Apple computers, for example, do not
support a fixed serial port rate or
hardware flow control (Clear to
Send/Request to Send signaling).
Software Settings
Hardware flow control: Select your
software's option for hardware flow
control. Many programs combined CTS/RTS
as one option.
NOTE: All 100% IBM-compatible computers
support hardware flow control. Some
software supports both hardware and
software flow control, but requires you
to turn off the kind you're not using.
Check your software manual.
38.4K or 19.2K bps: Set a high data
rate between the modem and the computer.
A rate of 19.2K bps is required to make
a 14.4K bps connection, however 38.4K
bps provides the greatest efficiency
when a call is under error control and
data compression.
NOTE: If you are certain that your
software, computer, and serial card (if
you have one) can handle 57.6K bps, you
can use this higher speed. We recommend
that you use this speed only if
necessary; you could lose data if part
of your system can't handle 57.6K bps.
If you're not sure of your system's
capabilities, use 38.4K bps, which is
efficient and reliable.
Fixed Rate: Many programs that support
a fixed serial port rate control this
function with an Auto Baud Detect
toggle. Toggle Auto Baud Detect OFF and
the software data rate will remain high,
even if the phone connection is as low
as 300 bps. If your software calls this
Locking the Port Speed, select this
option.
Modem Settings
&H1 Clear to Send Hardware flow
control: the modem sends CTS
signals to the computer or
terminal to control the data
flow. Flow control is required
for error control and when the
serial port rate is higher than
the connection rate. (The &H2
setting, software flow control,
may affect data reliability. See
Example 2 in the next section,
Alternative Settings.)
&R2 Request to Send hardware flow
control: the computer or
terminal sends RTS signals to the
modem to control the data flow.
&B1 The modem's serial port rate is
fixed at the rate of the last AT
command. It does not switch to
match the phone connection rate
when the modem connects with a
remote modem at a lower rate.
Your software must first be set
to a fixed rate, as shown under
the previous heading, Software
Settings.

If your software supports the &H1, &R2
and &B1 options, we recommend that you
make them your power-on and reset
defaults by writing them to nonvolatile
memory. See Page 3-9.
NOTE: The next section, Alternative
Settings, shows how to set the modem if
your software does not support the
above options. Also included are
recommended settings if you will
normally use software flow control but
plan to use an Xmodem-type protocol,
and guidelines on transferring files
that are already compressed.

ALTERNATIVE SETTINGS

1.Your software doesn't support Clear
to Send, but supports XON/XOFF
signaling.
&H2 Software flow control: the
modem sends Ctrl-S and Ctrl-Q
(XOFF/XON) characters to the
computer or terminal to control
the flow of data.
&B1 As above, under Recommended
Settings, providing your
software supports a fixed
serial port rate.
WARNING: Software flow control is not
recommended because Ctrl-S or Ctrl-Q
characters that occur in a file, or
in a file transfer protocol such as
Zmodem, may be misinter-preted and
dropped from the data stream by the
modem or receiving computer. Set the
modem to &H2 or &H3 only if you are
transferring text files.
2.Your machine or software doesn't
support Clear to Send, and you're
using an Xmodem-type file-transfer
protocol.
&H0 Factory setting. Flow control
disabled. Do not use software
flow control (&H2), because the
protocol uses the Ctrl-S and
Ctrl-Q characters that will be
misinterpreted as flow control
characters, and you risk losing
data.
&B0 Factory setting. The serial
port rate switches to match the
connection rate of each call.
Recommended because there is no
flow control. Be sure also to
set your communications
software to switch its rate.
Turn ON the Auto Baud Detect
option, unlock the serial port,
or select whatever setting the
program requires.
&M0 Error control disabled;
recommended because there is no
flow control.
CAUTION: Many Xmodem-type protocols
are available. However, keep the
following limitations in mind.
ù Most of these protocols perform
error control, which makes them
safe for calls at all rates from
14.4K down to 300 bps. Ymodem-G,
however, should not be used with
the above modem settings, because
its response to errors is to abort
the call. Earlier versions of
Zmodem did not perform error
control and should also be avoided.
Current versions of Zmodem,
however, are highly recommended.
See Throughput Guidelines in
Chapter 4 or appendix A for more
guidelines.
ù Because flow control is disabled,
the data packets transferred by the
protocol should be less than 1,000
bytes in size, and should not be of
the sliding-window type. Review
the protocol documentation before
using the protocol. If the packets
are too large, and there is no flow
control, you risk losing data.
3.Your system doesn't support either
Clear to Send or XON/XOFF signaling.
&H0 Factory setting. Flow control
disabled.
&B0 Factory setting. The serial
port rate switches to match the
connection rate of each call.
Required because there is no
flow control.
&M0 Error control disabled,
required because there is no
flow control.
CAUTION: We recommend that the modem
settings just described never be used
for calls above 2400 bps unless
you're using an error-control file-
transfer protocol. See the
cautionary notes under Example 2.
4.Your software does not support a
fixed rate at the serial port
interface.
&B0 Factory setting, variable
serial port rate: this rate
switches to match the
connection rate of each call.
This does not affect error
control or flow control.
NOTE: You will not gain the
throughput efficiency that
occurs when the serial port
rate is fixed at a higher rate
than the connection rate. In
addition, at the factory
setting for data compression,
&K1, the modem disables
compression when the connection
rate is set to &B0. When the
serial port and connection
rates are equal, data
compression gives no advantage.
In fact, data compression
operations add time to the
call.
5.You are calling a non-MNP modem.
S27=16Disable MNP handshaking. A non-
MNP modem may misinterpret the
MNP link request and prevent a
successful connection. If the
remote modem uses V.42 error
control, the modems will
connect under V.42 error
control. Otherwise, they
connect without any error con
trol. Note that this applies
only if you are calling a non-
MNP modem.
6.You are transferring already
compressed files.
&K3 This disables MNP compression,
which does not work
successfully with files that
are already compressed. If the
remote modem is able to use
V.42 bis compression, you will
gain optimal throughput.

DATA FORMAT

Your communications software and the
remote communications software must be
set to the same word length, parity, and
number of Stop bits. Information
Services and Bulletin Boards make this
information readily available. If you
don't know what the remote system
requires, phone first to find out. If
you have trouble connecting with a
remote system, the reason may be the
wrong word length/parity/Stop bit
combination.
The Sportster modem is set at the
factory to a 7-bit word length, even
parity, and 1 Stop bit. Some
communications programs use a shorthand
method to refer to this format: 7-E-1.
If you wish to call a remote system that
requires a different format, set your
software to the correct parameters
before you attempt to dial out. When
the modem receives the dial command, it
detects the new data format from the AT
command prefix.
One Start bit is universal and not
programmable. The other allowable
options are listed in the following
table; with the Start bit they form a
ten-bit data unit.

Table 3.1_Allowable Data Formats

Word Parity Stop
Length (1 Bit) Bits
7 Even, Odd, 1
Mark, Space
7 None 2
8 None 1

STORING DEFAULTS IN NONVOLATILE MEMORY

Write your default configuration to
nonvolatile memory (NVRAM) with the &W
command. First, set your software to
the desired communications parameters,
for example:
Serial port rate 38.4K bps
Word length 8
Parity None
Stop bits 1
The following command example sets the
modem for the current session, and
stores the settings inserted before &W
as defaults. These include the above
parameters that the modem detects from
the rate and format of the AT command
prefix.
AT &B1 &H1 &W
As long as DIP switch 7 is UP (OFF), the
modem loads the defaults from NVRAM at
power-on and reset, including the rate
and format defaults. Be sure to type &W
last in the string, before pressing the
Enter key.
DIALING

Use the following command format,
beginning with the AT prefix and issued
by pressing . The maximum number
of characters in a command string is 40.
The modem defaults to pulse dialing:
the T in the command enforces tone
dialing.
ATDT phonenumber
To redial the number, you can use the
repeat command.
A/
This command causes the modem to re-
execute the command in the command
buffer. If you've sent an additional
command to the modem, that command now
occupies the buffer.