LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 43 of 125
1.9
Serial Communication
1.9.1
Asynchronous serial interface (UART)
The UART interface is a 9-wire unbalanced asynchronous serial interface that provides an AT commands
interface, GPRS data and CSD data, software upgrades.
The UART interface provides RS-232 functionality conforming with
ITU-T V.24 Recommendation
[4], with CMOS
compatible signal levels: 0 V for low data bit or ON state, and 2.85 V for high data bit or OFF state. An external
voltage translator (Maxim MAX3237) is required to provide RS-232 compatible signal levels. For the detailed
electrical characteristics refer to the
LEON-G100 / LEON-G200
Data Sheet
LEON-G100 / LEON-G200 modules are designed to operate as a GSM/GPRS modem, which represents the data
circuit-terminating equipment (DCE) as described by the
ITU-T V.24 Recommendation
[4]. A customer application
processor connected to the module through the UART interface represents the data terminal equipment (DTE).
The signal names of the LEON-G100 / LEON-G200 UART interface conform to
ITU-T V.24
Recommendation
The UART interface includes the following lines:
Name
Description
Remarks
DSR
Data set ready
Module output, functionality of ITU-T V.24 Circuit 107 (Data
set ready)
RI
Ring Indicator
Module output, functionality of ITU-T V.24 Circuit 125
(Calling indicator)
DCD
Data carrier detect
Module output, functionality of ITU-T V.24 Circuit 109 (Data
channel received line signal detector)
DTR
Data terminal ready
Module input, functionality of ITU-T V.24 Circuit 108/2 (Data
terminal ready)
Internal active pull-up to 2.85 V enabled.
RTS
Ready to send
Module hardware flow control input, functionality of ITU-T
V.24 Circuit 105 (Request to send)
Internal active pull-up to 2.85 V enabled.
CTS
Clear to send
Module hardware flow control output, functionality of ITU-T
V.24 Circuit 106 (Ready for sending)
TxD
Transmitted data
Module data input, functionality of ITU-T V.24 Circuit 103
(Transmitted data)
Internal active pull-up to 2.85 V enabled.
RxD
Received data
Module data output, functionality of ITU-T V.24 Circuit 104
(Received data)
Table 16: UART pins
UART interface pins ESD sensitivity rating is 1 kV (HBM JESD22-A114F). A higher protection level could
be required if the lines are externally accessible on the application board. A higher protection level can
be achieved mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) on the lines
connected to these pins if they are externally accessible on the application board.
1.9.1.1
UART features
UART interface is controlled and operated with:
AT commands according to
3GPP TS 27.007
AT commands according to
3GPP TS 27.005
AT commands according to
3GPP TS 27.010
u-blox AT commands
