Contents:

Connecting to your ISP

Using the AT Command Set

Upgrading your Modem

Modes of Operation

Dialing, Answering, and Hanging Up

Working with Memory

Controlling Result Code Displays

Controlling EIA-232 Signaling

Accessing and Configuring the Courier 56K Corporate Modem Remotely

Controlling Data Rates

Dial Security

Flow Control

Handshaking, Error Control, Data Compression, and Throughput

Displaying Querying and Help Screens

Testing the Connection

Dedicated/Lease Line and Synchronous Applications

Troubleshooting

Appendixes

S-Registers

Alphabetic Command Summary

Flow Control Template

Result Code Meanings and Sets

Technical Information

V.25 bis Reference

ASCII Chart

Fax Information for Programmers

Viewing LEDs

Regulatory Information

Glossary

Courier 56K Corporate Modem Command Reference

Controlling Data Rates

This chapter contains information about:

Overview

You can set the Courier 56K Corporate modem to use fixed or variable serial port rates and fixed or variable connection rates. Serial port rates pertain to data transferred between your computer and the Courier 56K Corporate modem. Connection rates pertain to data transferred between the Courier 56K Corporate modem and the device at the other end of a connection.

 

Serial Port Rates

You set a fixed serial port rate to get the highest possible throughput and the best performance. Set a variable rate to allow the Courier 56K Corporate modem to match the connection rate.

Your software must support fixed or variable serial port rates.

Note: Your software may use terms such as locked serial port (fixed rate) or autobaud (variable rate).

To allow your modem
Set the serial port rate as
Command
To change its serial port rate to match the connection rate.
Variable
AT&B0
To always communicate with an attached device at the rate at which you have set the terminal or software, regardless of the connection rate.
Fixed
AT&B1 (Default)
For the greatest throughput, set the serial port to 230400, 115200, 57600, or 38400 bps for high-speed calls, and to at least 9600 bps for 2400-bps calls.

To shift its serial port rate to a rate that you specify using your communications software (for example, 38.4 Kbps) when the Courier 56K Corporate modem connects in ARQ mode.

If the connection is not under error control, the Courier 56K Corporate modem behaves as if it was set to &B0 and switches its serial port rates to match the connection rate of each call.

Fixed for ARQ calls
AT&B2

To implement this feature, first set your software to the desired rate. Then send AT&B2&W to the modem.

The Courier 56K Corporate modem stores the rate of the command in NVRAM along with the current settings. The Courier 56K Corporate modem checks NVRAM for the specified serial port rate each time it makes an ARQ connection.

When saving subsequent configurations to NVRAM, be sure your software is set to your selected serial port rate so the correct rate is maintained.

Variable for non-ARQ calls when answering only.

Refer to the Handshaking, Error Control, Data Compression, and Throughput chapter of the Contents section for more information about ARQ

Note: The serial port rate MUST be equal to or higher than the Connection rate (&Nn).

 

Connection Rates

You can set the Courier 56K Corporate modem to a fixed or variable connection rate for data calls. Set a variable rate to have the Courier 56K Corporate modem negotiate with the remote device for the highest possible connection rate. Set a fixed rate to connect only at a specified rate. You might use a fixed rate to filter calls for security or other reasons.

To allow your modem to
Set connection rate as
Command
Negotiate for the highest possible rate.
Variable
AT&N0
Connect only if the remote device is operating at the rate you specify. See below.
Fixed
AT&N1-AT&N16

 

To connect at this rate
Command
To connect at this rate
Command
300 bps
AT&N1
32.0 Kbps
AT&N20
1200 bps
AT&N2
33.333 Kbps
AT&N21
2400 bps
AT&N3
34.666 Kbps
AT&N22
4800 bps
AT&N4
36.0 Kbps
AT&N23
7200 bps
AT&N5
37.333 Kbps
AT&N24
9600 bps
AT&N6
38.666 Kbps
AT&N25
12.0 Kbps
AT&N7
40.0 Kbps
AT&N26
14.4 Kbps
AT&N8
41.333 Kbps
AT&N27
16.8 Kbps
AT&N9
42.666 Kbps
AT&N28
19.2 Kbps
AT&N10
44.000 Kbps
AT&N29
21.6 Kbps
AT&N11
45.333 Kbps
AT&N30
24.0 Kbps
AT&N12
46.666 Kbps
AT&N31
26.4 Kbps
AT&N13
48.0 Kbps
AT&N32
28.8 Kbps
AT&N14
49.333 Kbps
AT&N33
31.2 Kbps
AT&N15
50.666 Kbps
AT&N34
33.6 Kbps
AT&N16
52.0 Kbps
AT&N35
28.0 Kbps
AT&N17
53.333 Kbps
AT&N36
29.333 Kbps
AT&N18
54.666 Kbps
AT&N37
30.666 Kbps
AT&N19
56.0 Kbps
AT&N38


Example: Sending AT&N8 will only allow connections with remote devices that are operating at 14.4 Kbps.

 

Controlling Link Speeds With &N and &U

You can use the &N and &U commands to control link speeds.

Controlling Link Speeds

Use the following table to determine how to use &N and &U commands:

To limit the
Use
Specific connect speed
AT&N
Range of possible connect speeds
AT&N and AT&U

Note: The default values for &N and &U are 0. If you change these values, you will limit the speeds at which you can connect. USRobotics recommends that you do not alter these values.

Specifying the Connect Speed

The &N command allows you to specify the connect speed. If a remote modem attempts to connect to your Courier 56K Corporate modem at a speed different from &N, your Courier 56K Corporate modem will not allow it to connect.

To limit the
Use this command
Where x is
Highest possible connect speed
AT&N=x
A value from 0 to 38

Note: For a complete list of connect speeds, see the table in the &N and &U Command Values section of this chapter.

Limiting a Range of Possible Connect Speeds

By setting &N and &U values, you can limit the range of speeds at which your Courier 56K Corporate modem connects. If a remote modem does not connect to your Courier 56K Corporate modem at a range between the speeds designated by the &N and &U commands, your Courier 56K Corporate modem will not allow it to connect.

The link speed associated with the &U argument CANNOT be greater than the link speed associated with &N argument.

Use the following table to understand the relationship between &U and &N commands:

If &U
And &N
Then your modem
Equals zero Equals zero Connects at the highest possible speed.
Equals zero Is greater than zero Connects at the &N speed only.
Is greater than zero Is greater than zero and greater than &U Connects at the highest possible speed in the range from &U to &N.
Is greater than zero Equals zero Not allowed.

 

&N and &U Command Values

Use the following table for a complete list of &N and &U link speeds and their associated indexes:

 
Link Speed Index Link Speed Index
Highest 0 32000 20
300 1 33333 21
1200 2 34666 22
2400 3 36000 23
4800 4 37333 24
7200 5 38666 25
9600 6 40000 26
12000 7 41333 27
14400 8 42666 28
16800 9 44000 29
19200 10 45333 30
21600 11 46666 31
24000 12 48000 32
26400 13 49333 33
28800 14 50666 34
31200 15 52000 35
33600 16 53333 36
28000 17 54666 37
29333 18 56000 38
30666 19    

 

Configuring The High Speed LED

You can configure your Courier 56K Corporate modem to alert you when it reaches 56K speeds. Use the following S69 setting to configure the HS (High Speed) LED:

 
To do this
Command
Configure the HS LED to turn red when your modem reaches speeds over 33.3 kbps.
ATS69=12

 

Setting DTE Rate To 230 Kbps

The DTE rate of your Courier 56K Corporate modem has been increased to 230 kbps to enhance throughput. Your modem must be attached to a serial port capable of this speed to achieve this rate.

Note: This command is only supported with modems attached to high speed serial cards.