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Chapter 1 – Introduction

CDMA 1xEV-D0 AT Commands Reference Guide (Document S000482B) 12

Data Buffers

Data being transmitted or received is buffered in several ways depending on the mode and nature of the

connection. Some caution must be taken when disconnecting to ensure that any buffered data in the

modem has been properly processed prior to breaking the connection.

Specific settings for buffer controls are described in the relevant commands and registers. Normal

configuration of the modem does not require you to adjust these settings.

Speed Buffering

The simplest form of buffering allows for line speed differences and busy conditions between the host

(DTE) and modem and between the modem and the remote terminal or network. The network side of the

connection can have rates up 153.6 kbps, while the local host connection can be at one of many different

speeds from 300 bps to 230.4 kbps.

Where large amounts of data are being exchanged, local hardware flow control must be used to prevent

buffer overflows. To reduce packet loss, the CDMA protocol incorporates flow control on the network

connection.

Command Handling

AT can be issued as a command without parameters. It acts like a “ping” to the modem and always gives a result

code of “OK”. If there is no response from the modem, try issuing ATQ0 (Quiet mode off). If this fails, try the

“+++” escape sequence or resetting the modem.

Commands may be entered in upper or lower case.

Concatenation

More than one command can be included in a single line, although some commands or their parameters

must be placed at the end of the line. When concatenating commands, a space between basic

commands is optional. Where extended commands (those beginning with a non-alphabetic character)

are concatenated, they must be separated by a semi-colon.

Commands are executed in the order entered. If a command results in the ERROR result code, the

balance of the command line is ignored. Only one result code is returned for the entire command line.

Parameters

Most AT commands support one or more parameters, usually a number. Parameter ranges are specified

in the reference.

Commands that normally accept a single numeric option switch ([n]) and are issued without that

parameter assume a value of zero (0).

Defaults shown in the command tables are those for the factory settings of the modem and are not the

defaults assumed for a command issued without parameters.

Registers

Some registers are read only. If an attempt is made to write to a read only register, the ERROR result

code is returned.

Some registers store the setting of commands. Changing the register is equivalent to changing the

command setting. See the Table of S-Registers for the standard default values.

See the Table of Stored Profile Settings for the factory defaults.

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Multitech CDMA Guía de usuario Pagina 12