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Chapter 1 – Introduction

CDMA 1xEV-D0 AT Commands Reference Guide (Document S000482B) 13

Responses and Result Codes

Most commands return only a result code however some commands request information, which is provided by

the modem as a response prior to the result code.

Possible Result Codes

Result codes are not shown in the command tables unless special conditions apply. Generally the result

code OK is returned when the command has been executed. ERROR may be returned if parameters are

out of range, and is returned if the command is not recognized, or the command is not permitted in the

current mode, state, or condition of the modem.

See the Table of Result Codes, giving both the numeric and verbose results.

Human vs. Machine Interface

The AT command interface was designed for human interaction. When an intelligent host is managing a

modem, the interface may need to be altered; result code words replaced with numbers, for example.

Framing characters (line feeds and carriage returns) must be properly understood to ensure the host

system properly parses the responses and result codes.

As shipped the modem is configured with these settings:

• Echo enabled (E1): which causes the modem to echo characters received from the host back to

it while in command state. The backspace is echoed as <BS>.

• Quiet result codes disabled (Q0): which enables the modem to issue result codes following

commands. Quiet on (Q1) suppresses result codes entirely; responses remain unaffected.

• Verbose result codes (V1): which provides results in English text appended with <CR><LF>.

Verbose off (V0) returns the results as ASCII numeral codes. Numeric codes are much easier to

process.

With Echo on (E1 - the default), data received from the local host while in command state is echoed back

to the host. This can present problems to machine control, which is not interested in an echo of its own

commands to the modem. In some configurations the echo should be turned off (E0).

The configuration for most machine-controlled hosts is more likely to be set to Echo Off, and Verbose Off

or possibly Quiet On.

Framing

The framing of the response and result elements by <CR><LF> depends heavily on the settings of the

modem. In particular the settings of Verbose (V) and Quiet (Q) modes alter the framing of both

responses and result codes.

These elements are normally formatted for human reading with a terminal program, however users

wishing to have software read and adjust to these responses and result codes must understand how

they are framed.

Framing Characters

The modem will frame replies with carriage return and line feed characters as they are defined in

registers S3 and S4 respectively. These are normally the ASCII values 13 <CR> and 10 <LF>.

For the purposes of the discussion here, they are referred to as <CR> and <LF>.

If there are any problems determining the exact framing of the response and result codes, use a

protocol analyzer to monitor the exchanges.

Response Framing

Regardless of command settings, responses are in ASCII text with a trailing <CR><LF>. Where a

response has more than one line, each line is terminated with a <CR><LF>. The programmer must know

the number of lines expected in the response.

The setting of Verbose (V) on (=1) triggers a leading <CR><LF> prior to the first line of the response. If

Verbose is off (=0), there are no leading characters prior to the first line of response.

The setting of Quiet (Q) has no impact on responses.

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