Specifications

LEON-G100/G200 - System Integration Manual
GSM.G1-HW-09002-C Preliminary System description
Page 45 of 75
The DTR line is set by default to the OFF state at the UART initialization, at the end of the boot sequence after
the module switch on. 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.
By default the RI and the DCD lines are set to the OFF state at UART initialization, at the end of the boot
sequence. The RI line is then held by the module in the OFF state until an incoming call or SMS is received. The
DCD line is held in the OFF state until a data call is accepted.
During an incoming call the RI line is switched from the OFF state to the ON state with a 4:1 duty cycle and a 5
second period (ON for 1 second, OFF for 4 second, see Figure 29), 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. When the
data call is accepted, the module is set to ON state and the serial line DCD sends the CONNECT<communication
baudrate> to the DTE. DTE sends data through the DCE and the GSM network to the remote DCE-DTE system
and data communication can be performed as for outgoing data calls.
Figure 29: RI behavior at incoming call
The RI line is used to notify an SMS arrival. When the SMS arrives the RI line switches from OFF to ON for 1
second (see Figure 30).
Figure 30: RI behavior at SMS arrival
1.11.1.3 UART application circuits
Full RS-232 Functionality
For complete RS-232 functionality conforming to [3] in DTE/DCE serial communication, the complete UART
interface of the module (DCE) must be connected to the DTE as described in Figure 31.
SMS arrives
time [s]
0
RI ON
RI OFF
1s
SMS
time [s]
0
RI ON
RI OFF
1s
1s
time [s]
151050
RI ON
RI OFF
Call incomes
1s
time [s]
151050
RI ON
RI OFF
Call incomes