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LARA-R2 series - System Integration Manual

UBX-16010573 - R02

Objective Specification

System description

Page 39 of 148

DTR signal behavior

The

DTR

module input line is set by default to the OFF state (high level) at UART initialization. The module then

holds the

DTR

line in the OFF state if the line is not activated by the DTE: an active pull-up is enabled inside the

module on the

DTR

input.

Module behavior according to

DTR

status can be changed by AT command (for more details, see

u-blox AT

Commands Manual

[2], AT&D command description).

If AT+UPSV=3 is set, the

DTR

line is monitored by the module to manage the power saving configuration (for

more details, see section 1.9.1.4 and

u-blox AT Commands Manual

[2], AT+UPSV command):



When an OFF-to-ON transition occurs on the

DTR

input, the UART is enabled and the module is forced to

active-mode. After ~20 ms, the switch is completed and data can be received without loss. The module
cannot enter low power idle-mode and the UART is enabled as long as the

DTR

is in the ON state



If the

DTR

input line is set to the OFF state by the DTE, the UART is disabled (held in low power mode) and

the module automatically enters low power idle-mode whenever possible

DCD signal behavior

If AT&C1 is set, as it is by default, the

DCD

module output line is set by default to the OFF state (high level) at

UART initialization. The module then sets the

DCD

line according to the carrier detect status: ON if the carrier is

detected, OFF otherwise.
In case of voice calls,

DCD

is set to the ON state when the call is established.

In case of data calls, there are the following scenarios regarding the

DCD

signal behavior:



Packet Switched Data call

: Before activating the PPP protocol (data mode) a dial-up application must

provide the ATD*99***<context_number># to the module: with this command the module switches from
command mode to data mode and can accept PPP packets. The module sets the

DCD

line to the ON state,

then answers with a CONNECT to confirm the ATD*99 command. The

DCD

ON is not related to the context

activation but with the data mode



Circuit Switched Data call

: To establish a data call, the DTE can send the ATD<number> command to the

module which sets an outgoing data call to a remote modem (or another data module). Data can be
transparent (non reliable) or non transparent (with the reliable RLP protocol). When the remote DCE accepts
the data call, the module

DCD

line is set to ON and the CONNECT <communication baudrate> string is

returned by the module. At this stage the DTE can send characters through the serial line to the data
module which sends them through the network to the remote DCE attached to a remote DTE

The

DCD

is set to ON during the execution of the +CMGS, +CMGW, +USOWR, +USODL AT commands

requiring input data from the DTE: the

DCD

line is set to the ON state as soon as the switch to binary/text

input mode is completed and the prompt is issued;

DCD

line is set to OFF as soon as the input mode is

interrupted or completed (for more details see the

u-blox AT Commands Manual

[2]).