LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 47 of 125
DSR signal behavior
If AT&S0 is set, the
DSR
module output line is set by default to ON state (low level) at UART initialization and is
then always held in the ON state.
If AT&S1 is set, the
DSR
module output line is set by default to OFF state (high level) at UART initialization. The
DSR
line is then set to the OFF state when the module is in command mode or in online command mode and is
set to the ON state when the module is in data mode.
The above behavior is valid for both Packet-Switched and Circuit-Switched Data transfer.
DTR signal behavior
The
DTR
module input line is set by default to OFF state (high level) at UART initialization. The
DTR
line is then
held by the module 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 depends on the AT command
configuration (see
u-blox AT Commands Manual
[2], &D AT command).
DCD signal behavior
If AT&C0 is set, the
DCD
module output line is set by default to ON state (low level) at UART initialization and is
then always held in the ON state.
If AT&C1 is set, the
DCD
module output line is set by default to OFF state (high level) at UART initialization. The
DCD
line is then set by the module in accordance with the carrier detect status: ON if the carrier is detected, OFF
otherwise. In case of voice call
DCD
is set to ON state when the call is established. For a data call there are the
following scenarios:
GPRS data communication
: 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. Please note that the
DCD
ON is not
related to the context activation but with the data mode
CSD 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
In case of a voice call
DCD
is set to ON state on all the serial communication interfaces supporting the
AT command interface. (including MUX virtual channels, if active).
DCD
is set to ON during the execution of a command requiring input data from the DTE (all the
commands where a prompt is issued; see AT commands +CMGS, +CMGW, +USOWR, +USODL,
+UDWNFILE in
u-blox AT Commands Manual
[2]). The
DCD
line is set to 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.
DCD
line is kept to ON state even during the online command state to indicate that the data call is still
established even if suspended, while if the module enters command mode
DSR
line is set to OFF state.
For more details refer to DSR signal behavior description.
In case of scenarios for which the
DCD
line setting is requested for different reasons (e.g. SMS texting
during online command state), the
DCD
line changes to guarantee the correct behavior for all the
scenarios. For instance, in case of SMS texting in online command state, if the data call is released, the
