LISA-U2 series - System Integration Manual
UBX-13001118 - R19
Early Production Information
System description
Page 54 of 175
1.9.2
Asynchronous serial interface (UART)
The UART interface is a 9-wire unbalanced asynchronous serial interface that provides AT commands interface,
PSD and CSD data communication.
The module firmware can be upgraded over the UART interface using the u-blox EasyFlash tool or by means of
AT command (for more details see section 3.1 and
Firmware update application note
UART interface provides RS-232 functionality conforming to the ITU-T V.24 Recommendation (more details
available in
ITU Recommendation
[3]), with CMOS compatible signal levels: 0 V for low data bit or ON state, and
1.8 V for high data bit or OFF state. For detailed electrical characteristics see
LISA-U2 series Data Sheet
The LISA-U2 modules are designed to operate as an HSPA cellular modem, which represents the data circuit-
terminating equipment (DCE) as described by the
ITU-T V.24 Recommendation
[3]. A customer application
processor connected to the module through the UART interface represents the data terminal equipment (DTE).
The signal names of the LISA-U2 modules UART interface conform to the
ITU-T V.24 Recommendation
UART interfaces include the following lines:
Name
Description
Remarks
DSR
Data set ready
Module output
Circuit 107 (Data set ready) in ITU-T V.24
RI
Ring Indicator
Module output
Circuit 125 (Calling indicator) in ITU-T V.24
DCD
Data carrier detect
Module output
Circuit 109 (Data channel received line signal detector) in ITU-T V.24
DTR
Data terminal ready
Module input
Circuit 108/2 (Data terminal ready) in ITU-T V.24
Internal active pull-up to
V_INT
(1.8 V) enabled.
RTS
Ready to send
Module hardware flow control input
Circuit 105 (Request to send) in ITU-T V.24
Internal active pull-up to
V_INT
(1.8 V) enabled.
CTS
Clear to send
Module hardware flow control output
Circuit 106 (Ready for sending) in ITU-T V.24
TxD
Transmitted data
Module data input
Circuit 103 (Transmitted data) in ITU-T V.24
Internal active pull-up to
V_INT
(1.8 V) enabled.
RxD
Received data
Module data output
Circuit 104 (Received data) in ITU-T V.24
GND
Ground
Table 27: 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, close to accessible points.
