Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 60 of 182
established. For a data call there are the following scenarios (see the u-blox AT Commands Manual [2]
for the definition of the interface data mode, command mode and online command mode):
 PSD 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.
 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.
☞ For 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 that requires input data from the DTE (all the
commands where a prompt is issued; see AT commands +CMGS, +CMGW, +USOWR, +USODL,
+UDWNFILE in the 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 mode to indicate that the data call
is still established even if suspended, while if the module enters command mode, the DSR line is
set to OFF state. For more details, see the DSR signal behavior description.
☞ For scenarios where the DCD line setting is requested for various reasons (e.g. SMS texting during
online command mode), the DCD line changes to guarantee the correct behavior for all the
scenarios. For instance, in case of SMS texting in online command mode, if the data call is
released, the DCD line will be kept to ON until the SMS command execution is completed (even if
the data call release would request the DCD setting to OFF).
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 second period (ON for 1 second, OFF for 4 seconds, see Figure 26), 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.
Figure 26: RI behavior during an incoming call
1s
time [s]
151050
RI ON
RI OFF
Call incomes
1s
time [s]
151050
RI ON
RI OFF
Call incomes