Z02215 datasheet(19/74 Pages) ZILOG

19 / 74 page

Z02215

Single Chip Modem with Integrated Controller, Data Pump, and AFE

PS001907-0904

AT Command Set

ON-LINE

After successfully completing Handshaking the modems enter the ON-LINE state.

When a modem is in the ON-LINE state, data received from its terminal is sent

over the telephone line to the other modem. Data received from the other modem

is sent to the terminal.

COMMAND

If the terminal sends a special escape sequence to a modem in the ON-LINE

state, the modem enters the COMMAND state. During COMMAND state the

modem maintains the connection with the other modem but does not pass data

between the terminal and the other modem. Instead, data received from the termi-

nal is treated as AT commands in the same way as if the modem was in the Idle

state. The modem can be returned to the ON-LINE state by the O command. Data

received from the other modem while a modem is in COMMAND state is dis-

carded unless the modem can buffer it for display on the terminal when the

modem re-enters the ON-LINE state.

Retrain

During a telephone line connection, the modem tries to remain synchronized with

the remote modem by adapting to changes in telephone line connection and

bridging transient noises such as call waiting, analog switching and cross talk. In

V.22bis and higher speed data modes, if the modem loses synchronization with

the remote modem data can not be received until synchronization is restored by a

process called Retraining. During Retraining the modem accepts data and com-

mands from the terminal but does not transmit data to, or receive data from, the

other modem.

AT Command Set

Command lines are typed to the modem from the terminal when the modem is in

the IDLE or COMMAND state. The modem does not execute any of the com-

mands in a command line until after the command line is ended by the end-of-line

character <CR>. A command line is a string of characters starting with the A and T

characters and ending with a special end-of-line character, <CR>. Characters

typed before the AT are ignored. Command lines contain, at most, 40 characters

after the AT. The modem does not execute any of the commands in a command

line that is too long.

To echo command line characters, use the E1 command.

Z02215 Datasheet(PDF) 19 Page - Zilog, Inc.