LISA-C2 series and FW75-C200 - System Integration Manual
UBX-13000620 - R21
Early Production Information
System description
Page 27 of 103
Name
Description
Remarks
RxD
Received data
Module data output
Circuit 104 (Received data) in ITU-T V.24
FW75-C200 - Internal active pull-up to
V_INT
(2.8 V) interface.
LISA-C200- Internal active pull-up to
V_INT
(1.8 V) interface.
GND
Ground
Table 13: UART interface signals
The UART interface pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higher
protection level could be required if the lines are externally accessible on the application board. Higher
protection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on
the lines connected to these pins.
1.9.2.1
RI signal behavior
The RI behaviour on LISA-C200 is different than on GSM/UMTS/HPSA modules, such as LEON, SARA, and
LISA-U series modules. On LISA-C200, RI toggles between voice call, SMS, and data session, while on
ublox’s GSM/UMTS/HSPA based modules, RI does not toggle while in a data session, unless there is an
incoming voice call or SMS. The reason for the difference is that CDMA technology does not support
multiple transport types (circuit switched and packet switched) at the same time, where GSM/UMTS/HSPA
does support them.
The RI line is available on the first serial interface ASC0 (see also Section 3.10). The signal serves to indicate
incoming calls and other types of URCs (Unsolicited Result Code). Although not mandatory for use in a host
application, it is strongly suggested to connect the RI line to an interrupt line of the application. In this case, the
application can be designed to receive an interrupt when a falling edge on RI line occurs. This solution is most
effective, particularly, for waking up a host/application from power saving mode.
The behavior of the RI line varies with the type of event. When a voice/SMS/fax/data call comes in, the RI line
goes low for 1 s and high for another 4 s. Every 5 seconds the ring string is generated and sent over the /RXD0
line.
Figure 10: URC transmission for voice/fax/data
If there is a call in progress and call waiting is activated for a connected handset or hands free device, the RI line
switches to ground in order to generate acoustic signals that indicate the waiting call.
All other types of Unsolicited Result Codes (URCs) also cause the RI line to go low, however for 1 second only.
