Novatel Expedite User manual

AT Command Set
Reference Guide
for
Expedite and Merlin
Wireless IP Modems
PS-01016529
UNRELEASED
Release 2.1
Friday, May 7, 1999

The information disclosed herein is the exclusive property of NOVATEL WIRELESS TECHNOLOGIES
LTD. and is not to be disclosed without the written consent of NOVATEL WIRELESS TECHNOLOGIES
LTD. No part of this publication may be reproduced or transmitted in any form or by any means including
electronic storage, reproduction, execution or transmission without the prior written consent of NOVATEL
WIRELESS TECHNOLOGIES LTD. The recipient of this document, by its retention and use, agrees to
respect the security status of the information contained herein.
This document is intended for limited circulation.
The information contained in this document is subject to change without notice and should not be
construed as a commitment by NOVATEL WIRELESS TECHNOLOGIES LTD. unless such commitment
is expressly given in a covering document.
© Copyright NOVATEL WIRELESS TECHNOLOGIES LTD. (1999)

REVISION HISTORY
REV# ECO# EFF. DATE DESCRIPTION PREPARED APPROVED
1 99010 990505 Initial release. D. Barber S. Smilar
2.0 99024 990705 Updated to include new features for
TV01-02, including Friends Mode,
Quiet mode and Stack Check
features.
D. Barber S, Smilar
2.1 Added registration mode and out-of-
service sleep commands. Added
index of AT commands.

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Table of Contents
INTRODUCTION.................................................................................................................................................... 6
Scope....................................................................................................................................................................... 6
PHYSICAL INTERFACE ....................................................................................................................................... 7
Protocol................................................................................................................................................................ 7
Software Interface.................................................................................................................................................. 8
AT Command Mode........................................................................................................................................... 8
Command format................................................................................................................................................ 8
Result format....................................................................................................................................................... 8
Data Mode Description...................................................................................................................................... 9
Internal Stack Description ............................................................................................................................... 10
UDP Mode Description.................................................................................................................................... 11
TCP Mode Description..................................................................................................................................... 12
DTR Control Description.................................................................................................................................. 14
Push Technology.............................................................................................................................................. 15
Slip Mode........................................................................................................................................................... 16
Point to Point Protocol (PPP).......................................................................................................................... 17
Data Transmission Mode................................................................................................................................18
Data Reception Mode...................................................................................................................................... 19
Sleep Mode Description................................................................................................................................... 20
Sleep Mode Feature Enable/Disable............................................................................................................. 21
Out-of-service Sleep Mode ............................................................................................................................. 22
Power-up Default Mode................................................................................................................................... 25
Set Hardware Configuration............................................................................................................................ 26
Profile Configuration Commands................................................................................................................... 27
Program Mode.................................................................................................................................................. 28
Local Echo......................................................................................................................................................... 29
Response Format............................................................................................................................................. 30
Programmable I/O............................................................................................................................................ 31
Soft Reset.......................................................................................................................................................... 33
Side Preference................................................................................................................................................ 34
Password........................................................................................................................................................... 35
Escape Sequence ............................................................................................................................................ 36
Hardware Flow Control.................................................................................................................................... 37
Disconnect (Hang-up)...................................................................................................................................... 38
Restore Factory Defaults................................................................................................................................. 39
Line Speed and Format................................................................................................................................... 40
View Active Profile............................................................................................................................................ 42
Save Current Profile......................................................................................................................................... 43
Destination IP Address/Port............................................................................................................................ 44
Debug Mode...................................................................................................................................................... 45
Auto Answer (TCP Listen)............................................................................................................................... 46
Connection Establishment Time-out.............................................................................................................. 47
Data Forwarding Idle Time-out....................................................................................................................... 48
Data Forwarding Idle Character ..................................................................................................................... 49
UDP Half Open Mode...................................................................................................................................... 50
Status Reporting............................................................................................................................................... 51
Local IP Address/Port...................................................................................................................................... 53
Service ID Preference...................................................................................................................................... 55
Channel Scan Mode......................................................................................................................................... 56
Channel List ...................................................................................................................................................... 58

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Service ID Preference...................................................................................................................................... 59
CDPD Operating Version................................................................................................................................60
Wireline Compatibility...................................................................................................................................... 61
Set DTR Control ............................................................................................................................................... 62
DTR Mode Setting............................................................................................................................................ 63
DSR Control Setting......................................................................................................................................... 64
TCP Timer......................................................................................................................................................... 65
Identity Registers.............................................................................................................................................. 66
Description:........................................................................................................................................................ 66
Query Network Connection Status................................................................................................................. 67
Last network registration error code.............................................................................................................. 70
Authentication Parameter................................................................................................................................71
Query Current RSSI Value.............................................................................................................................. 72
Query Current Block Error Rate (BLER)....................................................................................................... 73
Current RF Channel in use ............................................................................................................................. 74
Cell Site ID in Use ............................................................................................................................................ 75
Area Color Code in Use................................................................................................................................... 76
Power Level Query........................................................................................................................................... 77
Symbol Error Rate Query................................................................................................................................78
Power Product................................................................................................................................................... 79
Authentication Failures Query......................................................................................................................... 80
Dial (Connection Setup)................................................................................................................................... 81
ADC Monitoring................................................................................................................................................. 83
Ping Command................................................................................................................................................. 86
Power Boost...................................................................................................................................................... 87
Message Waiting.............................................................................................................................................. 88
Internal MRU Setting........................................................................................................................................ 89
TCP Suspension Enable ................................................................................................................................. 90
Call Progress Result Mode ............................................................................................................................. 91
Answer............................................................................................................................................................... 92
Telnet Echo....................................................................................................................................................... 93
Modem Identification........................................................................................................................................ 94
Friends Mode.................................................................................................................................................... 95
Stack Check...................................................................................................................................................... 97
Quiet Mode........................................................................................................................................................ 98
Registration Mode ............................................................................................................................................ 99
Fixed Parameters........................................................................................................................................... 100
Unsupported Commands.............................................................................................................................. 101
Unsupported Functions.................................................................................................................................. 101
Appendix A: AT Command Set Quick Reference....................................................................................... 102
Index of AT Commands..................................................................................................................................... 106

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INTRODUCTION
This document is intended to provide the serial AT Command Interface provided by Expedite
Wireless IP Modem for embedded OEM applications. The Expedite Wireless IP modem provides
a connection-oriented service so that existing OEM application protocols can be used. In addition,
the capability to switch the unit to Serial-Line-Internet-Protocol (SLIP) or Point-to-Point-Protocol
(PPP) modes are provided so that new protocols can be developed within the OEM application.
This document describes the Novatel Wireless Expedite Wireless IP Modem. The Expedite
Wireless IP modem is an OEM-module designed for integration into a host product to provide
wireless data communication capability via the CDPD (Cellular Digital Packet Data) Network. It
features internal TCP and UDP IP stacks as well as SLIP and PPP protocols for an external stack
and provisions for using “Sleep Mode” to extend the operating time of battery powered devices.
Scope
The scope of this document is limited to providing information on the various AT commands which
can be used on Novatel CDPD products as well as a brief summary of some of the standard AT
commands which are not supported. Internal design issues, detailed operating instructions and
cost information is not included in this document.

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PHYSICAL INTERFACE
Protocol
CDPD System Specification Part 400 Version 1.1 (CDPD Forum Inc.) This is the protocol stack
for the Expedite Wireless IP Modem:
Ph
y
sical
MAC
MDLP
SNDCP
IP
SLIP PPP UDP TCP
AT Interface
Communication Driver
CDPD
La
y
ers
Host
OEM
A
pp
lication
La
y
ers
To Host
The Expedite Wireless IP Modem does not support V.42 compression in SNDCP.
The TCP/UDP interface is capable of supporting up to 3 sessions simultaneously1.
The AT-command set described herein is derived from “CDPD Implementor Guidelines”, Release 1.12. It
contains a subset of the commands described in Part 2014 that are supported by the Novatel Expedite
Wireless IP Modem.
For the purposes of this specification, “NRM” refers to the Novatel Expedite Wireless IP Modem; “Host”
refers to the OEM application controller.
1This is provided to solve the problem presented by delays encountered when closing a TCP session. That is, in order to process
Host transactions in rapid succession (and since it is required to establish a new TCP session for each transaction) it is
necessary to establish a new TCP session before the previous one has had a chance to close.
2CDPD Forum makes no representations about the suitability of any material, comprising the CDPD system specification (or any
derivative work incorporating any element thereof) for any purpose; it being provided “as is” and without any warranties
whatsoever, express or implied. The CDPD Forum shall not be responsible for any damages of any kind related to the use of
the CDPD system specification (or any derivative work incorporating any element thereof), including without limitation,
actual, direct, indirect, incidental, consequential, special, or general damages.

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Software Interface
A brief description of those functions specific to the Expedite Wireless IP Modem is described here.
AT Command Mode
AT commands and responses are active in command mode only; as determined by the state of the DSR
line. Command mode behavior conforms to ANSI/TIA/EIA-602-1992 section 5, with the limitations stated
below. The AT command set is a subset of the AT command set defined in ANSI/TIA/EIA-602 and in the
CDPD System Specification Part 2014 Version 1.1, section 4.
Command format
Note the following limitations:
- The termination character is fixed as CR (ASCII 13).
- Command line editing is supported (BS, ASCII 08 only).
- Command line repeats (A/) is not supported.
- The rules described below for buffering and flow control also apply to command mode. The Host
should not transmit a single AT command which exceeds the buffer length (256 characters). In
addition, the Host should wait until all responses associated with an AT command string have been
received before issuing another AT command.
- Abortion of command-in-progress is not supported.
- Default command parameters are accepted for the last command on a command line only.
Result format
The format of result code responses is determined by the ATV command setting.
In terse mode, the result code is sent as a single ASCII character followed by a carriage return (ASCII 13)
character.
In verbose mode, a descriptive text message is sent followed by a carriage return. The following result
codes are emitted by the NRM:
Terse
mode Verbose mode Description of Command
0 OK Command accepted.
1 CONNECT Connection established.
2 RING Network origination indication.
3 NO CARRIER Connection terminated, not established or command aborted.
4 ERROR Invalid command parameter/state (e.g. DTR must be active before ATD can be
accepted.)
5 NO SOCKETS No free TCP sockets within S7 seconds.
6 NO DIALTONE CDPD link not established.
7 BUSY Refused by destination or network, OR: Operation in progress.
8 NO ANSWER No response received from the destination within S7 seconds.
9 HELLO Issued at power on/reset.

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Data Mode Description
The modem contains an integrated TCP/IP protocol stack. It is accessed via AT commands that put the
modem into either a TCP or UDP data communications mode. If the application host contains a TCP/IP
stack, PPP or SLIP can be used to transfer IP packets between the application host and the modem.
The Data Terminal Ready (DTR) line is used by the modem as a qualifier for its operation in a data mode,
TCP, UDP, SLIP or PPP. The DTR line is to be asserted before entering a data mode to indicate to the
modem that the host computer is available for operation. The DTR line is de-asserted to terminate a data
session. The modem will not sustain a data mode session without DTR being active. The use of DTR
can be overridden by setting register S211 to 1: the equivalent of asserting DTR permanently.
The DSR Signal is driven by the modem to indicate the existence of a data session. When the local host
asserts DTR, the modem will respond with the DSR signal to indicate that the modem has entered data
mode. DSR is de-asserted to indicate that the modem has exited data mode.
The NRM provides Host and Network originated access to the connection-oriented service using TCP/IP.
Host origination is accomplished via the DIAL (ATDT) command. Upon successful completion of the DIAL
command (i.e. CONNECT result code), the NRM switches to TCP-Data mode. DTR must be asserted
prior to issuing the ATDT, ATDP, AT\ASLIP or AT\APPP. If this is not followed the modem will not engage
the session in a manner where it can be sustained. The NRM signals a network origination to the Host
using the RING result code. Failure to have DTR asserted while in “Listen” mode, network origination, will
result in a dropped session. The PAD functions are active during TCP-Data mode only, however, the
data buffering functions apply in all modes.
For Listen mode applications, the modem must see DTR asserted when the TCP Session request is
received. If DTR is not asserted the session request will be rejected. When the DTR signal is asserted,
the modem will issue a RING followed by a CONNECT to indicate the beginning of an incoming data
session. Here RING indicates the source of the session as being a remote server while the CONNECT
indicates the transition from AT Command mode to Data mode. . In this mode, the NRM will “Listen” for
TCPP packets with port numbers which match that specified with the NRM’s IP address (re: S110). Any
TCP packets received in AT-CDPD mode, or packets received in TCP-Data mode without a matching port
number, are rejected by the NRM with no indication to the Host. DTR can be used to terminate the
session or the remote server can initiate the termination.
A session may be terminated by the Host de-asserting the DTR line. The remote host may also terminate
a session. Connection status is maintained on the DSR line. Once the session has been terminated, the
NRM returns to AT-CDPD mode. Note that session termination is the only method to return to AT-CDPD
mode3.
For UDP/IP, a connection-oriented service is “fabricated” within the NRM. The DIAL command (ATDP) is
used to place the NRM into UDP-Data mode. In this mode, the NRM will “Listen” for UDP packets with
port numbers which match that specified with the NRM’s IP address (re: S110). Any UDP packets
received in AT-CDPD mode, or packets received in UDP-Data mode without a matching port number, are
rejected by the NRM with no indication to the Host. In UDP-Data mode, the port number for transmitted
UDP packets is specified with the destination address associated with the DIAL command. Only the Host
Origination and Host Termination scenarios described above apply to UDP operation. The DTR and DSR
lines, and the PAD functions, operate as in TCP-Data mode.
3The Hayes compatible escape sequence is not supported.

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Internal Stack Description
IP (Internet Protocol) is the basic network protocol that routes packets on an IP network. CDPD networks
and the Internet are IP networks. Transport protocols deliver packets between applications. Transport
protocols use the IP service to deliver data packets between network devices.
In order for an application to communicate across a network, it will first open a port on the local device.
The IP address of the local device and this port number becomes the unique address for this application,
and is sometimes referred to as a socket. When the local application communicates with a distant
application, it will send a packet addressed to the IP address and port number of that remote application.
This address is the destination address of the packet. The packet will also contain the source address, the
IP address and port number of the local application. The remote application may use the source address
of the packet received to communicate back to the local application.
There are two common transport protocols used in TCP/IP networks:

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UDP Mode Description
User Datagram Protocol is a basic transport protocol that provides a best-effort, connectionless delivery
service with minimum overhead. The protocol does not guarantee delivery of packets. There is no
checking or retransmission of the data packets. It does provide minimum overhead as it only adds the
source and destination port numbers to the header. Since the protocol is unreliable, the application must
provide checking, acknowledgments and retransmissions if the data is critical. In many applications, the
data is not critical because updates are sent periodically and occasional losses can be tolerated.
UDP sessions may be originated by the local application host or by the network. The DTR signal must be
asserted or S211=1 (pretend DTR is always asserted) for the unit to enter into a data communications
session. The session is terminated by dropping DTR or resetting the unit.
UDP Modes of Operation
Command: ATS82 = <mode>
Where <mode> = Timer value in seconds
0 = Regular mode
1 = Not used (reserved)
2 = Half-Open mode
Originating a UDP Session
A session is originated by the application host issuing the ATD (Dial) command:
ATDPnnn.nnn.nnn.nnn/ppppp
ATDP specifies a UDP session. nnn.nnn.nnn.nnn is the destination IP address and ppppp is the
destination application port number. If no port is specified then a port number of 0 is assumed. It should
be noted that UDP and TCP make extensive use of port numbers, please be aware that the modem will
use the port number as a criteria for accepting and passing data to the host application.
CONNECT [terse 1] result code will be issued and all ensuing data sent from the host application will be
assembled into a UDP packet and transmitted to the destination application.
ERROR [terse 4] result code will be generated if the modem is not currently registered on a CDPD
network.
PAD (Packet Assembly and Disassembly) function will transmit data when the inter-character idle time-out
occurs or when the PAD buffer is full. (256 or 512 bytes). The idle time-out is specified in register S50 in
1/10 seconds.
Receiving Data - Once the session is started, any packets sent to the modem's IP address with the port
number specified in register S110 will be processed and the data portion will be transmitted over the serial
link to the host application. Any packets received with a different port number specified will be discarded.
Termination - The session is terminated by dropping DTR or resetting the unit.

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TCP Mode Description
Transport Control Protocol, is a reliable, connection-oriented transport protocol that uses
acknowledgments and retransmissions to guarantee delivery. This is an obvious advantage for
applications where the data is critical and the application cannot provide the required reliability. There is
more overhead in the protocol to provide this reliability, making it less efficient than UDP. For larger data
transfers, TCP is the easiest protocol to use to get reliable service.
TCP sessions may be originated by the local application host or by the network. The DTR signal must be
asserted or S211=1 (pretend DTR is always asserted) for the unit to enter into a data communications
session. The session is terminated by powering the modem off, dropping DTR or by the remote host
terminating the connection. If the session is terminated by a power down, the remote host may not tear
down its part of the session properly, leaving the remote host waiting for further information for that
session. This can pose problems for some applications. Care in session tear down is essential for
reliable operation.
TCP Modes of Operation
TCP Listen mode is established by having S0=1 when the modem powers up. . The port specified in
S110 will be used for the TCP Listen mode. The DTR signal must be asserted or S211=1 (ignore signal on
DTR pin and proceed as if DTR is always asserted) for the unit to enter into a data communications
session. When a connection request for the correct port is received by the modem, the modem will
establish the connection notify the local host with:
Verbose Terse
RING 2
CONNECT 1
and begin the TCP session.
Termination - A TCP connection is terminated by dropping DTR, or by the remote end of the TCP
connection terminating the session.
Originating a TCP Session
A session is originated by the host application by issuing the ATD (Dial) command:
ATDTnnn.nnn.nnn.nnn/ppppp
ATDT specifies a TCP session. nnn.nnn.nnn.nnn is the destination IP address and ppppp is the
destination application port number. The modem will attempt to establish a connection with the destination
host. If it is successful, a CONNECT [terse 1] result code will be issued and all ensuing data sent from the
app host will be assembled into a TCP packet and transmitted to the destination application.
ERROR [terse 4] result code will be generated if the modem is not currently registered on a CDPD
network.
Connection Failure will be signaled by a BUSY [terse 7] result code, and may be caused by one of the
following:
- Wrong IP address or port number
- The destination device does not have a TCP Listen process open on the port specified.
- The destination host already has a connection established with another client on the specified port.

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- Connection failed to complete within the time specified in register S7 (sec). Normal values are about
30 seconds, but is very dependent upon the application requirements. Many applications, which
provide their own time-out for connection failure, will have this value set to 60+ seconds.
PAD (Packet Assembly and Disassembly) function will transmit data when the inter-character idle time-out
occurs or when the PAD buffer is full. (256 or 512 bytes). The idle time-out is specified in register S50 in
1/10 seconds.
Receiving Data - Once the session is started, any packets sent to the modem's IP address with the port
number specified in register S110 will be processed and the data portion will be transmitted over the serial
link to the host application. Any packets received with a different port number specified will be discarded.
Termination - A TCP connection is terminated by dropping DTR or by the remote end of the TCP
connection terminating the session.

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DTR Control Description
The Data Terminal Ready (DTR) line is used by the modem as a qualifier for its operation in a data mode,
TCP, UDP, SLIP or PPP. The DTR line is to be asserted before entering a data mode to indicate to the
modem that the host computer is available for operation. The DTR line is de-asserted to terminate a data
session. The modem will not sustain a data mode session without DTR being active. The use of DTR
can be overridden by setting register S211 to 1: the equivalent of asserting DTR permanently.
The DSR Signal is driven by the modem to indicate the existence of a data session. When DTR is
asserted by the local host, the modem will respond with the DSR signal to indicate that the modem has
entered data mode. DSR is de-asserted to indicate that the modem has exited data mode.
For Listen mode applications, the modem must see DTR asserted when the TCP Session request is
received. If DTR is not asserted the session request will be rejected. When the DTR signal is asserted,
the modem will issue a RING followed by a CONNECT to indicate the beginning of a incoming data
session. Here RING indicates the source of the session as being a remote server while the CONNECT
indicates the transition from AT Command mode to Data mode. . In this mode, the NRM will “Listen” for
TCPP packets with port numbers which match that specified with the NRM’s IP address (re: S110). Any
TCP packets received in AT-CDPD mode, or packets received in TCP-Data mode without a matching port
number, are rejected by the NRM with no indication to the Host. DTR can be used to terminate the
session or the remote server can initiate the termination.
A session may be terminated by the Host using the DTR line. The remote host may also terminate a
session. Connection status is maintained on the DSR line. Once the session has been terminated, the
NRM returns to AT-CDPD mode. Note that session termination is the only method to return to AT-CDPD
mode4.
The DTR line de-asserted can also be optionally used to power the modem off in addition to the
termination of the session. If the S211 register is set to 4, then the de-asserting of the DTR line will make
the modem terminate any current data session, perform a de-registration with the network and power itself
off.
4The Hayes compatible escape sequence is not supported.

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Push Technology
To receive data while the modem is unattended by the host, the modem has been incorporated with the
means to receive the data packet, determine the type of message and the source IP address. This push
technology feature can be enabled or disabled by setting or resetting register S250. The modem can
signal the host that there are messages queued up, waiting to be retrieved by the host, using any or all of
the following signals. The “message waiting” signal can be asserted when a message arrives and will be
de-asserted when all messages have been retrieved or deleted. In the case of multiple messages, the
“message waiting” signal will be asserted when the first arrives and will only be de-asserted when all
messages have been retrieved. Another signal, the “alert” signal, can also be used to provide a 500msec
pulse to the host on its associated pin for each message that arrives. These signals can be made
available on any of the programmable pins of the interface. Their assignment is made using the
programmable GPIO features of the Expedite Wireless IP Modem.
The modem can hold up to 4 messages, determined by reading register S251, before the buffer overflows
and message data is lost. When the host accesses the modem to retrieve the stored messages, the host
first determines which messages it wants to retrieve based upon the source IP address. The host can
discard messages by setting register S254. This will cause the current message to be flushed from the
queue and the next message made available to the host.
PUSH Technology Enable
ATS250? Query Wake Up Protocol State
ATS250=1 Enable Push Technology
ATS250=0 Disable Push Technology
ATS251? Query Number of Pending Messages
Response [0..4]
ATS252? Query First Push Message
Response [IPaddress/port]
Format nnn.nnn.nnn.nnn/xxxxx
ATS253? Query Type of First Push Message
Response [0, 1] 0 indicates UDP, 1 indicates TCP
ATS254=1 Discard Current Message

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Slip Mode
Description:
The command to enter Serial Line Internet Protocol mode (SLIP) is used when an external stack
configuration is needed. SLIP is useful if the stack resides in the host computer, multiple sessions and
complete control over all aspects of each session can be obtained. SLIP is one of the more common
protocols used for splitting the functionality between the modem and the host. SLIP does, however,
require certain parameters to be set up prior to activating a session. SLIP does not extract the IP address
from the modem. This must be set up in dial-up-networking before starting. SLIP is less flexible than
Point to Point Protocol (PPP) which is quickly winning over most users.
The SLIP session is usually controlled by DTR, unless the modem has been configured to ignore DTR by
programming register S211. DTR, when used, must be asserted to initiate a session and de-asserted to
terminate a session. If the modem has been programmed not to use DTR Control, then the command
AT\ASLIP can be sent without asserting DTR. To exit SLIP in this case, the host must either power down
the modem or use the escape sequence. To terminate a SLIP session, DTR must be de-asserted or the
escape sequence can be activated or the modem can be powered down.
Format:
AT\ASLIP The command to enter SLIP mode
Validity:
Slip can only be entered from Command Mode. In Program or Diagnostic modes, the modem is not
actively connected to the network.
Other Considerations:
While a modem can enter SLIP mode from command mode at any time, the intent of SLIP is to connect to
the network. Until there is a network connection established and the modem has registered, it is better to
delay entering SLIP mode as you may report errors that will only persist until the modem registers. It is
generally recommended that the host check the status of the modem before proceeding with a SLIP
connection. The Status can be checked using the “ATS57?” command.
Related Topics:
Enter PPP Mode, DTR Control, Program Mode, Data Mode, Diagnostic Mode. Checking Status, Escape
Sequence

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Point to Point Protocol (PPP)
Description:
The command to enter Point to Point Protocol mode (PPP) is used when an external stack configuration is
needed. PPP is useful if the stack resides in the host computer, providing multiple sessions and complete
control over all aspects of each session. PPP is quickly becoming the new standard for dial-in-networking.
PPP provides more flexibility and less items that need to be explicitly set.
The PPP session is usually controlled by DTR, unless the modem has been configured to ignore DTR by
programming register S211. DTR, when used, must be asserted to initiate a session and de-asserted to
terminate a session. If the modem has been programmed not to use DTR Control, then the command
AT\APPP can be sent without asserting DTR. To exit PPP in this case, the host must either power down
the modem or use the escape sequence. To terminate a PPP session, DTR must be de-asserted or the
escape sequence can be activated or the modem can be powered down.
.
Format:
AT\APPP The command to enter PPP Mode
The response will be CONNECT or ERROR
The alternate command to use is SERVER
The response will be CLIENT
Validity:
PPP can only be entered from Command Mode. In Program or Diagnostic modes, the modem is not
actively connected to the network.
Other Considerations:
While a modem can enter PPP mode from command mode at any time, the intent of PPP is to connect to
the network. Until there is a network connection established and the modem has registered, it is better to
delay entering PPP mode as you may report errors that will only persist until the modem registers. It is
generally recommended that the host check the status of the modem before proceeding with a PPP
connection. The Status can be checked using the “ATS57?” command.
An alternate method of entering PPP mode is to send the word CLIENT to the modem. The modem will
respond with SERVER. This is NOT an AT command. It is neither preceded by an "AT" nor succeeded
by a CR. Exiting PPP mode is performed using the DTR control signal.
Related Topics:
SLIP Mode, DTR Control, Program Mode, Data Mode, Diagnostic Mode. Checking Status

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AT Command Specification-Expedite and Merlin
Wireless IP Modems
Data Transmission Mode
Packet Assembly
The NRM provides a local Packet Assembly and Disassembly (PAD) function. For transmission,
the character stream from the Host is assembled into packets for RF transmission under the
following conditions:
-Idle time-out: If the time between successive characters exceeds the time interval specified in
register S50, any pending data is assembled for transmission.
Buffering and Flow Control
The NRM has an input data buffer which is intended to be set larger than the longest transmit
message used by existing protocols in the Host. The size of this buffer is 578 characters.
If hardware flow control is disabled and, the NRM is formatting and transmitting data blocks
associated with a packet, the Host should not send additional data as this may cause input buffer
overflow. Buffer overflow will result in a loss of data with no indication to the Host. In order to
avoid data loss, it is recommended (and anticipated) that the Host application protocol operates
using a half-duplex ACK/NAK protocol. It should be expected that the Host acknowledgment
time-out should be set greater than that required for circuit-switched modem configurations. This
is to account for propagation delays through the NRM, CDPD base station and CDPD and Internet
networks.

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AT Command Specification-Expedite and Merlin
Wireless IP Modems
Data Reception Mode
Packet Disassembly
The NRM begins transmitting the character stream associated with a received packet to the Host
as soon as all the associated blocks have been received and processed.
Buffering and Flow Control
The NRM has an output data buffer which is intended to be set larger than the longest receive
message used by existing protocols in the Host application. The size of this buffer is 2144
characters.
When the NRM is sending the characters associated with a received packet to the Host, the
remote host processor should not send additional data as this may result in output buffer overflow.
NRM buffer overflow shall result in a loss of data with no indication to the Host or remote host. In
order to avoid data loss, it is recommended (and anticipated) that the Host application protocol
operates using a half-duplex ACK/NAK protocol. The remote host acknowledgment time-out
should be lengthened as described above.

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AT Command Specification-Expedite and Merlin
Wireless IP Modems
Sleep Mode Description
Sleep mode can be activated by sending the commands AT#ZZ=1, AT#ZZ=2 or deactivated by
the command AT#ZZ=0. Changes must be entered in program mode. The module should be
reset after changing the sleep mode activation since the module will have registered and informed
the network that it has sleep mode or not. The module will enter sleep mode, if activated, after the
inactivity timer has expired and a Network TEI notification message has been received by the
modem.
In areas with low signal strength or where the signal strength varies to a high degree, the unit may
not enter sleep mode in a regular fashion. The unit must have conditions where the unit can
decode the TEI notification messages from a reliable signal.
No notification message or signal is given to the host that sleep mode is engaged. The host must
assume that if the modem has been inactive for more than the number of seconds specified in the
inactivity timer that the modem has gone to sleep.
To wake the modem up from sleep mode, the wake-up signal can be asserted for a minimum of
10 ms or a break character of 20 ms in duration followed by a 2 ms pause or 2 character spaces
at 19200 bps can be sent. The module will de-assert CTS when entering sleep mode to inhibit the
host from sending data but will periodically assert CTS and check for incoming serial data from
the host to prevent any loss of data.
No indication is given to the module that the host is in sleep mode. The module will assume the
host is sleeping if the module is sleeping and send a break character to initialize communications
with the host.
There are two types of sleep mode implemented for this product:
i. Normal – in normal sleep mode, the modem will attempt to maximize its sleep time based
on the configuration of the network where it has registered. Practically, this means that if
the network supports a sleep time of 60 seconds, and allows 5 TEI notifications to be
missed without penalty, the modem could theoretically sleep for a minimum of 4 minutes.
ii. Short – in short sleep mode, the modem will attempt to sleep in short bursts of 5 seconds
and awaken to allow communication from the host. In this mode, CTS would normally be
deasserted so hosts would not normally attempt to send data until the CTS is asserted
again in 5 seconds when the modem wakes up for 400msec. This is the same operation
as in the NRM6812 products when AT#ZZ=2 and has been maintained for backward
compatibility.
Related Topics:
Sleep Mode Feature Enable/Disable