User's Manual

LISA-U1/LISA-H1 series - System Integration Manual
3G.G2-HW-10002-2 Advance Information System description
Page 46 of 116
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 and is set to the ON state when the
module is in data mode.
The above behavior is valide 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 cirtual 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 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.
RI signal behavior
The RI module output line is set by default to the OFF state (high level) at UART initialization. Then, during an
incoming call, the RI line is switched from OFF state to ON state with a 4:1 duty cycle and a 5 s period (ON for
1 s, OFF for 4 s, see Figure 22), until the DTE attached to the module sends the ATA string and the module
accepts the incoming data call. The RING string sent by the module (DCE) to the serial port at constant time
intervals is not correlated with the switch of the RI line to the ON state.